Common use of Signature Guarantee Clause in Contracts

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York ________________, ____ 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. (the "Company") 11 3/4% Senior Discount Notes due 2008 (the "Notes") Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ____________, ____ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. (the "Company") 11 3/4% Senior Discount Notes due 2008 (the "Notes") Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York _________________ , ____ 101 ▇▇▇▇The Chase Manhattan Bank ▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Telecopier No.: Chief Financial Officer Re(▇▇▇) ▇▇▇-▇▇▇▇ or 8178 Attention: Allegiance Telecom, Inc. Capital Markets Fiduciary Services The Chase Manhattan Bank London branch ▇▇▇▇▇▇▇ ▇▇▇▇▇ ▇ ▇▇▇▇▇▇ ▇▇▇▇ Street London E1 9YT Telecopier No.: 011-44-1202-34-7945 Attention: Capital Markets Fiduciary Services RE: CARRIER1 INTERNATIONAL S.A. (the THE "CompanyCOMPANY") 11 3/413 1/4% Senior Discount Notes due 2008 SENIOR EURO NOTES DUE 2009 (the THE "NotesNOTES") ------------------------------------------------ Dear Sirs: This letter relates to U.S. $Euro ________________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02(a) of the Indenture dated as of February 19, 1999 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------------------------ Authorized Signature 102 Signatory 20731870.1 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to NonFORM OF CERTIFICATE TO BE DELIVERED IN CONNECTION WITH TRANSFERS TO NON-QIB Accredited Investors ACCREDITED INVESTORS ____________, ____ The Chase Manhattan Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Telecopier No.: Chief Financial Officer Re(▇▇▇) ▇▇▇-▇▇▇▇ or 8178 Attention: Allegiance Telecom, Inc. Capital Markets Fiduciary Services The Chase Manhattan Bank London branch ▇▇▇▇▇▇▇ ▇▇▇▇▇ ▇ ▇▇▇▇▇▇ ▇▇▇▇ Street London E1 9YT Telecopier No.: 011-44-1202-34-7945 Attention: Capital Markets Fiduciary Services RE: CARRIER1 INTERNATIONAL S.A. (the THE "CompanyCOMPANY") 11 3/413 1/4% Senior Discount Notes due 2008 SENIOR EURO NOTES DUE 2009 (the THE "NotesNOTES") ------------------------------------------------ Dear Sirs: In connection with our proposed purchase of $___________Euro _______ aggregate principal amount at maturity of the Notes, in accordance with Section 2.08(a) of the Indenture referred to below, we confirm that:

Signature Guarantee. 101 EXHIBIT B --------- Form of Certificate The Bank of New York to be ------------------------- Delivered in Connection with ---------------------------- Legended Offshore Global Notes or Offshore Physical Notes --------------------------------------------------------- ________________, ,____ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇York, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionNew York 10286 Attention: Corporate Trust Trustee Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomAdvanced Lighting Technologies, Inc. (the "Company") 11 3/4[__]% Senior Discount Notes due 2008 (the "Notes") ----------------------------------------- Dear Sirs: This letter relates to U.S. $_______________ $ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture dated as of March [ __ ],1998 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ----------------------------------------- ____________, _,___ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY New York 10286 Attention: Corporate Trust Trustee Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomAdvanced Lighting Technologies, Inc. (the "Company") 11 3/4[__]% Senior Discount Notes due 2008 (the "Notes") ----------------------------------------- Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Chase Manhattan Bank of New York ________________, ____ 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Telecopier No.: Chief Financial Officer Re(▇▇▇) ▇▇▇-▇▇▇▇ or 8178 Attention: Allegiance Telecom, Inc. Capital Markets Fiduciary Services RE: CARRIER1 INTERNATIONAL S.A. (the THE "CompanyCOMPANY") 11 3/413 1/4% Senior Discount Notes due 2008 SENIOR DOLLAR NOTES DUE 2009 (the THE "NotesNOTES") Dear Sirs: This letter relates to U.S. $_______U.S.$________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02(a) of the Indenture dated as of February 19, 1999 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- --------------------------------- Authorized Signature 102 Signatory EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to NonFORM OF CERTIFICATE TO BE DELIVERED IN CONNECTION WITH TRANSFERS TO NON-QIB Accredited Investors __ACCREDITED INVESTORS __________, ____ The Chase Manhattan Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Telecopier No.: Chief Financial Officer Re(▇▇▇) ▇▇▇-▇▇▇▇ or 8178 Attention: Allegiance Telecom, Inc. Capital Markets Fiduciary Services RE: CARRIER1 INTERNATIONAL S.A. (the THE "CompanyCOMPANY") 11 3/413 1/4% Senior Discount Notes due 2008 SENIOR DOLLAR NOTES DUE 2009 (the THE "NotesNOTES") Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, in accordance with Section 2.08(a) of the Indenture referred to below, we confirm that:

Signature Guarantee. 101 EXHIBIT B --------- Form of Certificate The Bank of New York ------------------- _________________ , ____ 101 United States Trust Company of New York ▇▇▇▇ ▇▇▇▇ ▇▇/▇▇/ ▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇-▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Division: 25/th/ Floor Re: Allegiance TelecomRENAISSANCE MEDIA (LOUISIANA) LLC RENAISSANCE MEDIA (TENNESSEE) LLC RENAISSANCE MEDIA CAPITAL CORPORATION (together, Inc. (the "Company") 11 3/4------- 10% Senior Discount Notes due 2008 (the "Notes") --------------------------------------------------------------------- Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining ------------- restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture dated as of April 9, 1998 (the "Indenture") dated as of February 3, 1998 relating to the Notes, --------- we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- --------------------------------------- Authorized Signature 102 EXHIBIT C --------- Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ----------------------------------------- ____________, ____ The Bank United States Trust Company of New York 101 ▇▇▇ ▇▇▇▇ ▇▇/▇▇/ ▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇-▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Division: 25/th/ Floor Re: Allegiance TelecomRENAISSANCE MEDIA (LOUISIANA) LLC RENAISSANCE MEDIA (TENNESSEE) LLC RENAISSANCE MEDIA CAPITAL CORPORATION (together, Inc. (the "Company") 11 3/410% Senior Discount Notes due 2008 (the "Notes") ----------------------------------------------------------------------------- Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 A--13- EXHIBIT B Form of Certificate ---------------, ----- The Bank of New York ________________, ____ 101 ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇21-W New York, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionNew York 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomGeotek Communications, Inc. (the "Company") 11 3/412% Senior Discount Subordinated Convertible Notes due 2008 2001 (the "NotesSecurities") Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes Securities represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3March 5, 1998 1996 relating to the NotesSecurities, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes Securities could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate Legended Note for an unlegended certificate representing an identical principal amount at maturity of NotesSecurities, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of HolderTransferor] By: ---------------------------------- :____________ ------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Certain Transfers to Non-QIB Accredited Investors ____________---------------, ____ ----- The Bank of New York 101 ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West 21-W New York, NY New York 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomGeotek Communications, Inc. (the "Company") 11 3/412% Senior Discount Subordinated Convertible Notes due 2008 2001 (the "NotesSecurities") Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the NotesSecurities, we confirm that:

Signature Guarantee. 101 EXHIBIT B --------- Form of Certificate The Bank ------------------- -------, ---- United States Trust Company of New York ________________, ____ 101 ▇▇▇ ▇. ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇-▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Department Re: Allegiance TelecomITC/\DeltaCom, Inc. (the "Company") 11 3/411% Senior Discount Notes due 2008 2007 (the "Notes") --------------------------------------- Dear Sirs: This letter relates to U.S. $_______________ $ principal amount at maturity of Notes --------------- represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture dated as of June 3, 1997 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ----------------------------------------------- Authorized Signature 102 EXHIBIT C --------- Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ____________----------------------------------------- -------, ____ The Bank ---- United States Trust Company of New York 101 ▇▇▇ ▇. ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇-▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Department Re: Allegiance TelecomITC/\DeltaCom, Inc. (the "Company") 11 3/411% Senior Discount Notes due 2008 2007 (the "Notes") --------------------------------------- Dear Sirs: In connection with our proposed purchase of $__________________ $ ------------------ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York ________________, ____ 101 ▇FORM OF RULE 144A CERTIFICATE To: Bankers Trust Company Four ▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Corporate Trust Trustee Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom@Entertainment, Inc. (the "CompanyCOMPANY") 11 3/414 1/2% Senior Discount Notes due 2008 SENIOR DISCOUNT NOTES DUE 2009 (the THE "NotesNOTEs") Dear SirsLadies and Gentlemen: This letter relates to U.S. In connection with our proposed sale of $_______________ aggregate principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify confirm that we are (or we will hold such securities on behalf of) a person outside the United States sale has been effected pursuant to whom the Notes could be transferred and in accordance with Rule 904 of Regulation S promulgated 144A ("RULE 144A") under the U.S. Securities Act of 1933, as amendedamended (the "SECURITIES ACT"). AccordinglyWe are aware that the transfer of Notes to us is being made in reliance on the exemption from the provisions of Section 5 of the Securities Act provided by Rule 144A. Prior to the date of this Certificate we have been given the opportunity to obtain from the Company the information referred to in Rule 144A(d)(4), you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indentureand have either declined such opportunity or have received such information. You and the Company are entitled to rely upon this letter Certificate and are irrevocably authorized to produce this letter Certificate or a copy hereof to any interested party in any administrative or legal proceedings proceeding or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of HolderNAME OF PURCHASER] By: ---------------------------------- Authorized Signature 102 EXHIBIT C Form ----------------------------- Name: Title: Address: Date of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ____________, ____ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attentionthis Certificate: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. (the "Company") 11 3/4% Senior Discount Notes due 2008 (the "Notes") Dear Sirs: In connection with our proposed purchase of $__________________ __, ____ A-29 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- @ENTERTAINMENT, INC. TO BANKERS TRUST COMPANY Trustee -------------------- INDENTURE Dated as of January 27, 1999 --------------------- $256,800,000 aggregate principal amount at maturity of the Notes, we confirm that:maturity

Signature Guarantee. 101 EXHIBIT B Form [FORM OF TRANSFER CERTIFICATE FOR TRANSFER FROM GLOBAL SECURITY OR DEFINITIVE SECURITY TO DEFINITIVE SECURITY] (Transfers pursuant to Section 2.13(a)(1) or Section 2.13(a)(2) of Certificate the Indenture) ------------, ----- The Bank of New York ________________Chase Manhattan Bank, ____ 101 ▇as Registrar 600 ▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionSuite 1150 Houston, Texas 77002 Attn: Corporate Institutional Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Services Re: Allegiance Telecom, Inc. Transfer of $________ Principal Amount at Maturity of Zero Coupon Convertible Senior Notes due 2021 (the "CompanySecurities") 11 3/4% Senior Discount Notes due 2008 of Enron Corp. (the "NotesIssuer") Dear Sirs: Reference is hereby made to the Indenture dated as of February 7, 2001 (the "Indenture") between the Issuer and The Chase Manhattan Bank, as Trustee. Capitalized terms used but not defined herein shall have the meanings given them in the Indenture. This letter relates to U.S. $_______________ aggregate principal amount at maturity of Notes represented by a Note (the "Legended Note") Securities which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all held [in the manner provided for in the Indentureform of a [Definitive] [Global Security (CUSIP No. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors _____________ )]* in the name of [name of transferor] (the "Transferor") to effect the transfer of Securities. In connection with such request, ____ and in respect of such Securities, the Transferor does hereby certify that such Securities are being transferred in accordance with (i) the transfer restrictions set forth in the Securities and the Indenture and (ii) to a transferee that the Transferor reasonably believes is an institutional "accredited investor" (as defined in Rule 501 (a)(1), (2), (3) or (7) of Regulation D under the U.S. Securities Act of 1933, as amended) (an "Institutional Accredited Investor") which is acquiring such Securities for its own account or for one or more accounts, each of which is an Institutional Accredited Investor, over which it exercises sole investment discretion and (iii) in accordance with applicable securities laws of any state of the United States. [Name of Transferor], By: ----------------------------- Name: --------------------------- Title: -------------------------- Dated: -------------------------- EXHIBIT C [FORM OF NON-DISTRIBUTION LETTER FOR INSTITUTIONAL ACCREDITED INVESTORS] (Transfers pursuant to Section 2.13(a)(1) or Section 2.13(a)(2) of the Indenture) ----------------, --- The Bank of New York 101 Chase Manhattan Bank, as Registrar 600 ▇▇▇▇▇▇ ▇▇▇▇▇▇, Suite 1150 Houston, Texas 77002 Attn: Institutional Trust Services Enron Corp. 1400 ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. (the "Company") 11 3/4% Senior Discount Notes due 2008 (the "Notes") Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:Texas 77002

Signature Guarantee. 101 103 EXHIBIT B Form of Certificate The Bank of New York ________________, _,___ 101 ▇▇▇United States Trust Company of New York 114 ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Department Re: Allegiance TelecomPageMart Wireless, Inc. (the "Company") 11 3/41/4% Senior Subordinated Discount Notes due 2008 (the "Notes") Dear Sirs: This letter relates to U.S. $_______________ $ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3January 28, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------------------------------------ Authorized Signature 102 104 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ____________, _,___ The Bank United States Trust Company of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇114 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Corporate Trust Department Re: Allegiance TelecomPageMart Wireless, Inc. (the "Company") 11 3/41/4% Senior Subordinated Discount Notes due 2008 (the "Notes") Dear Sirs: In connection with our proposed purchase of $___________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 (Participant in recognized signature guarantee medallion program) Social Security Number or Taxpayer Identification Number: --------------------- 58 EXHIBIT B Form of Certificate The Bank of New York FORM OF CERTIFICATE ________________, ,____ 101 First Union National Bank 800 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇ - ▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Department Re: Allegiance TelecomMetrocall, Inc. (the "Company") 11 3/411% Senior Discount Subordinated Notes due 2008 (the "Notes") Dear SirsLadies and Gentlemen: This letter relates to U.S. $_______________ $ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.2 of the Indenture dated as of December 22, 1998 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate Legended Note for an unlegended certificate note representing an identical principal amount at maturity of the Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- -------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to NonFORM OF CERTIFICATE TO BE DELIVERED IN CONNECTION WITH TRANSFERS TO NON-QIB Accredited Investors ACCREDITED INVESTORS ____________, ,____ The First Union National Bank of New York 101 800 ▇▇▇▇ ▇▇▇▇▇▇ - ▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entiontention: Chief Financial Officer Corporate Trust Department Re: Allegiance TelecomMetrocall, Inc. (the "Company") 11 3/411% Senior Discount Subordinated Notes due 2008 (the "Notes") Dear SirsLadies and Gentlemen: In connection with our proposed purchase of $__________________ $ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York _______________ __, ____ 101 THE ▇▇▇▇ ▇▇ ▇▇▇ ▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or ▇▇ 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionttention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. IMPSAT CORPORATION (the "Company") 11 3/4% 12_% Senior Discount Notes due 2008 (the "NotesSecurities") Dear SirsLadies and Gentlemen: This letter relates to U.S. $_______________ principal amount at maturity of Notes Securities represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture (the "Indenture") dated as of February 3June 17, 1998 relating to the NotesSecurities, we hereby certify that we are (or we will hold such securities Securities on behalf of) a person outside the United States to whom the Notes Securities could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of NotesSecurities, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------ Authorized Signature 102 EXHIBIT C Form of Certificate to Be be Delivered in Connection with Transfers Pursuant to Non-QIB Accredited Investors Regulation S ___________ __, ____ The Bank of New York 101 THE ▇▇▇▇ ▇▇ ▇▇▇ ▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 W▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionttention: Chief Financial Officer Corporate Trust Administration Re: Allegiance Telecom, Inc. IMPSAT CORPORATION (the "Company") 11 3/4% 12_% Senior Discount Notes due 2008 (the "NotesSecurities") Dear SirsLadies and Gentlemen: In connection with our proposed purchase sale of $________U.S.$__________ aggregate principal amount at maturity of the NotesSecurities, we confirm that such sale has been effected pursuant to and in accordance with Regulation S under the Securities Act of 1933, as amended, and, accordingly, we represent that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York ______FORM OF CERTIFICATE __________, ____ 101 United States Trust Company of New York ▇▇▇ ▇. ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇-▇▇▇ention▇ Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇Department Re: ▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. COMMUNICATIONS CORPORATION (the THE "CompanyCOMPANY") 11 3/4% Senior Discount Notes due 2008 SENIOR NOTES DUE 2007 (the THE "NotesNOTES") Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture dated as of February 28, 1997 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------------------------------------ Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to NonFORM OF CERTIFICATE TO BE DELIVERED IN CONNECTION WITH TRANSFERS TO NON-QIB Accredited Investors __ACCREDITED INVESTORS __________, ____ The Bank United States Trust Company of New York 101 ▇▇▇ ▇. ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇-▇, ▇▇▇ Attention: Corporate Trust Department Re: ▇▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. COMMUNICATIONS CORPORATION (the THE "CompanyCOMPANY") 11 3/4% Senior Discount Notes due 2008 SENIOR NOTES DUE 2007 (the THE "NotesNOTES") Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate The Bank of New York ________________, ____ 101 ----------- ----- FelCor Suites Limited Partnership 545 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Suite 1300 Irving, Texas 75062 FelCor Suite Hotels, Inc. 545 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Suite 1300 Irving, Texas 75062 SunTrust Bank, Atlanta 58 E▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇ex Atla▇▇▇, ▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Department Re: Allegiance Telecom, Inc. FelCor Suites Limited Partnership (the "CompanyFelCor LP") 11 3/4[7 3/8% Senior Discount Notes due 2008 Due 2004] [7 5/8% Senior Notes Due 2007] (the "Notes") ------------------------------------------------------------- Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 of the Indenture (the "Indenture") dated as of February 3October 1, 1998 1997 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of HolderNAME OF HOLDER] By: ---------------------------------- ---------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ____________, ____ The Bank of New York 101 ------------- ---- FelCor Suites Limited Partnership 545 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Suite 1300 Irving, Texas 75062 FelCor Suite Hotels, Inc. 545 ▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇ Suite 1300 Irving, Texas 75062 SunTrust Bank, Atlanta 58 E▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇ex Atla▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Corporate Trust Department Re: Allegiance Telecom, Inc. FelCor Suites Limited Partnership (the "CompanyFelCor LP") 11 3/4[7 3/8% Senior Discount Notes due 2008 Due 2004] [7 5/8% Senior Notes Due 2007] (the "Notes") ------------------------------------------------------------- Dear Sirs: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm that:

Signature Guarantee. 101 EXHIBIT Exhibit B --------- Form of Certificate The Bank to Be Delivered upon Termination of New York ________________Restricted Period -------------------------------- On or after March 4, ____ 101 ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇▇▇ ▇▇▇▇ ▇▇ ▇▇▇▇▇▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Division Re: Allegiance TelecomBE Aerospace, Inc. (the "Company") 11 3/49-7/8% Senior Discount Subordinated Notes due 2008 2006 (the "NotesSecurities") Dear Sirs-------------------------------------------------------- Ladies and Gentlemen: This letter relates to U.S. $_______________ principal amount at maturity of Notes Securities represented by a Note the temporary global note certificate (the "Legended NoteTemporary Certificate") which bears a legend outlining restrictions upon transfer of such Legended Note). Pursuant to Section 2.01 201 of the Indenture dated as of January 24, 1996 relating to the Securities (the "Indenture") dated as of February 3, 1998 relating to the Notes), we hereby certify that (1) we are the beneficial owner of such principal amount of Securities represented by the Temporary Certificate and (or 2) we will hold such securities on behalf of) are a person outside the United States to whom the Notes Securities could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange issue a Certificated Security representing the legended certificate for an unlegended certificate representing an identical undersigned's interest in the principal amount at maturity of NotesSecurities represented by the Temporary Certificate, all in the manner provided for in by the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ----------------------------------------- Authorized Signature 102 EXHIBIT Exhibit C --------- Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Institutional Accredited Investors ------------------------------------------------------- ___________________, ____ The Bank of New York 101 BE Aerospace, Inc. ▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ 21 West New York▇▇▇▇▇ c/o Fleet National Bank of Connecticut ▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer Corporate Trust Division Re: Allegiance TelecomBE Aerospace, Inc. (the "Company") 11 3/49-7/8% Senior Discount Subordinated Notes due 2008 2006 (the "NotesSecurities") Dear Sirs------------------------------------------------------- Ladies and Gentlemen: In connection with our proposed purchase of $__________________ aggregate principal amount at maturity of the Notes, we confirm thatSecurities:

Signature Guarantee. 101 102 EXHIBIT B Form of Certificate The Bank of New York _____________ ____, ______ 101 THE ▇▇▇▇ ▇▇ ▇▇▇ ▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or ▇▇ 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇entiontention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. IMPSAT CORPORATION (the "Company") 11 3/412 1/8% Senior Discount Guaranteed Notes due 2008 2003 (the "NotesSecurities") Dear SirsLadies and Gentlemen: This letter relates to U.S. $_______________ principal amount at maturity of Notes Securities represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture (the "Indenture") dated as of February 3July 30, 1998 1996 relating to the NotesSecurities, we hereby certify that we are (or we will hold such securities Securities on behalf of) a person outside the United States to whom the Notes Securities could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of NotesSecurities, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------------------------------ Authorized Signature 102 103 EXHIBIT C Form of Certificate to Be be Delivered in Connection with Transfers Pursuant to Non-QIB Accredited Investors Regulation S -------------------------------------- ___________ ____, ______ The Bank of New York 101 THE ▇▇▇▇ ▇▇ ▇▇▇ ▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 W▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionttention: Chief Financial Officer Corporate Trust Administration Re: Allegiance Telecom, Inc. IMPSAT CORPORATION (the "Company") 11 3/412 1/8% Senior Discount Guaranteed Notes due 2008 2003 (the "NotesSecurities") Dear SirsLadies and Gentlemen: In connection with our proposed purchase sale of U.S. $__________________ aggregate principal amount at maturity of the NotesSecurities, we confirm that such sale has been effected pursuant to and in accordance with Regulation S under the Securities Act of 1933, as amended, and, accordingly, we represent that:

Signature Guarantee. 101 EXHIBIT B Form of Certificate FORM OF CERTIFICATE ------------------- The Bank of New York Chase Manhattan Bank. _______________ __, __19__ 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Attention: Chief Financial Officer Global Trust Services Re: Allegiance TelecomKMC Telecom Holdings, Inc. (the "Company") 11 3/4121/2% Senior Discount Notes due 2008 (the "Notes") Dear Sirs------------------------------------------ Ladies and Gentlemen: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture (the "Indenture") dated as of February 3January 29, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities Notes on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ----------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers Pursuant to Non-QIB Accredited Investors Regulation S ----------------------------------- The Chase Manhattan Bank. ___________ __, __19__ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇ention▇▇▇, ▇▇ ▇▇▇▇▇-▇▇▇▇ Attention: Chief Financial Officer Global Trust Services Re: Allegiance TelecomKMC Telecom Holdings, Inc. (the "Company") 11 3/4121/2% Senior Discount Notes due 2008 (the "Notes") Dear Sirs------------------------------------------ Ladies and Gentlemen: In connection with our proposed purchase sale of $__________________ U.S.$ aggregate principal amount at maturity of the Notes, we confirm that such sale has been effected pursuant to and in accordance with Regulation S under the Securities Act of 1933, as amended, and, accordingly, we represent that:

Signature Guarantee. 101 EXHIBIT B --------- Form of Certificate The ------------------- Norwest Bank of New York ________________Colorado, ____ 101 N.A. , 19 ---------- -- -- 1740 Broadway Denver, Colorado 80274-8693 Attenti▇▇: ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomICG Holdings, Inc. (the "Company") 11 3/45/8% Senior Discount Notes due 2008 2007 (the "NotesSecurities") Dear Sirs---------------------------------------- Ladies and Gentlemen: This letter relates to U.S. $_______________ $ principal amount --------------- at maturity of Notes Securities represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture (the "Indenture") dated as of February 3March 11, 1998 1997 relating to the NotesSecurities, we hereby certify that we are (or we will hold such securities Securities on behalf of) a person outside the United States to whom the Notes Securities could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of NotesSecurities, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ------------------------------------ Authorized Signature 102 EXHIBIT C --------- Form of Certificate to Be Delivered in Connection with Transfers Pursuant to NonRegulation S ----------------------------------- Norwest Bank Colorado, N.A. , 19 ---------- -- -- 1740 Broadway Denver, Colorado 80274-QIB Accredited Investors ____________, ____ The Bank of New York 101 8693 Attenti▇▇: ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance TelecomICG Holdings, Inc. (the "Company") 11 3/45/8% Senior Discount Notes due 2008 2007 (the "NotesSecurities") Dear Sirs--------------------------------------- Ladies and Gentlemen: In connection with our proposed purchase sale of $__________________ U.S.$ ------------ aggregate principal amount at maturity of the NotesSecurities, we confirm that such sale has been effected pursuant to and in accordance with Regulation S under the Securities Act of 1933, as amended, and, accordingly, we represent that:

Signature Guarantee. 101 EXHIBIT Exhibit B --------- Form of Certificate The ------------------- Norwest Bank of New York ________________Colorado, ____ 101 N.A. , 19 1740 Broadway ----------- -- -- ▇▇▇▇▇▇, ▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ -▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer and Escrow Services Re: Allegiance TelecomICG Services, Inc. (the "Company") 11 3/410% Senior Discount Notes due 2008 (the "Notes") Dear Sirs------------------------------------------------ Ladies and Gentlemen: This letter relates to U.S. $_______________ $ principal --------------- amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture (the "Indenture") dated as of February 312, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities Notes on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- --------------------------- Authorized Signature 102 EXHIBIT Exhibit C --------- Form of Certificate to Be Delivered in Connection with Transfers Pursuant to Non-QIB Accredited Investors ____________Regulation S ----------------------------------- Norwest Bank Colorado, ____ The Bank of New York 101 N.A. , 19 1740 Broadway ---------- -- -- ▇▇▇▇▇▇, ▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇-▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer and Escrow Services Re: Allegiance TelecomICG Services, Inc. (the "Company") 11 3/410% Senior Discount Notes due 2008 (the "Notes") Dear Sirs------------------------------------------------ Ladies and Gentlemen: In connection with our proposed purchase sale of $__________________ U.S.$ ---------- aggregate principal amount at maturity of the Notes, we confirm that such sale has been effected pursuant to and in accordance with Regulation S under the Securities Act of 1933, as amended, and, accordingly, we represent that:

Signature Guarantee. 101 Signature must be guaranteed by a participant in a recognized signature guaranty medallion program or other signature guarantor acceptable to the Trustee. EXHIBIT B Form of Certificate The Bank of New York FORM OF CERTIFICATE _________________, ____ 101 The Bank of New York ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇or 21 W▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇▇ 21st Floor New York, New York 10286 Attention: Corporate Trust Administration Protection One Alarm Monitoring, Inc. ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇entionAttention: Chief Financial Officer General Counsel Re: Allegiance TelecomProtection One Alarm Monitoring, Inc. (the "Company") 11 3/48 1/8% Senior Discount Notes due 2008 SENIOR SUBORDINATED NOTES DUE 2009 (the THE "NotesNOTES") Dear Sirs: This letter relates to U.S. $_______________ principal amount at maturity of Notes represented by a Note (the "Legended Note") which bears a legend outlining restrictions upon transfer of such Legended Note. Pursuant to Section 2.01 2.02 of the Indenture dated as of December 21, 1998 (the "Indenture") dated as of February 3, 1998 relating to the Notes, we hereby certify that we are (or we will hold such securities on behalf of) a person outside the United States to whom the Notes could be transferred in accordance with Rule 904 of Regulation S promulgated under the U.S. Securities Act of 1933, as amended. Accordingly, you are hereby requested to exchange the legended certificate for an unlegended certificate representing an identical principal amount at maturity of Notes, all in the manner provided for in the Indenture. You and the Company are entitled to rely upon this letter and are irrevocably authorized to produce this letter or a copy hereof to any interested party in any administrative or legal proceedings or official inquiry with respect to the matters covered hereby. Terms used in this certificate have the meanings set forth in Regulation S. Very truly yours, [Name of Holder] By: ---------------------------------- ----------------------------------- Authorized Signature 102 EXHIBIT C Form of Certificate to Be Delivered in Connection with Transfers to Non-QIB Accredited Investors ----------------------------------------- ____________, ____ The Bank of New York 101 ▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇ 21 West New York, NY 10286 Attention: Corporate Trust Administration Allegiance Telecom, Inc. 1950 ▇▇▇▇▇▇▇▇ ▇▇▇▇., ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇ention: Chief Financial Officer Re: Allegiance Telecom, Inc. (the "Company") 11 3/4% Senior Discount Notes due 2008 (the "Notes") Dear Sirs: In connection with our proposed purchase of $__________________ , ___ The Bank of New York ▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇, 21st Floor New York, New York 10286 Attention: Corporate Trust Administration Re: Protection One Alarm Monitoring, Inc. (the"Company") 8 1/8% Senior Subordinated Notes due 2009 (the "Notes") ------------------------------------------------------- Dear Sirs: In connection with our proposed purchase of $ aggregate principal amount at maturity of the Notes, we confirm that: