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                                                                 EXHIBIT 10.10


                              ASSIGNMENT OF RIGHTS

         This Assignment of Rights ( this "Assignment") is entered into as of
the 6th day of June 2001, by and between HM4 Teligent Qualified Fund, LLC, a
Delaware limited liability company, HM4 Teligent Private Fund, LLC, a Delaware
limited liability company, HM PG-IV Teligent, LLC, a Delaware limited liability
company, HM 4-SBS Teligent Coinvestors, LLC, a Delaware limited liability
company, and HM 4-EQ Teligent Coinvestors, LLC, a Delaware limited liability
company (each an "Assignor" and collectively the "Assignors"), and IDT
Investments Inc., a Nevada corporation (collectively, the "Assignee").

                                    RECITALS


         A. Each Assignor has transferred to the Assignee all of its shares of
preferred stock of Teligent, Inc., a Delaware corporation (the "Company").

         B. Each Assignor is a party to that certain Registration Rights
Agreement, dated December 3, 1999 (the "Registration Rights Agreement"), by and
between the Company and each of the entities listed on Schedule I thereto.
Capitalized terms not otherwise defined herein shall have the meaning ascribed
to such terms in the Registration Rights Agreement.

         C. Each Assignor desires to assign to the Assignee all of the
Assignors' rights, titles, and interests in and to the Registration Rights
Agreement.

                                   AGREEMENTS

         NOW, THEREFORE, in consideration of the covenants of the Assignee
hereunder and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto, intending to
be legally bound, hereby agree as follows:

         1. ASSIGNMENT. Pursuant to Section 5.09 of the Registration Rights
Agreement, each Assignor hereby sells, assigns, transfers, and conveys to the
Assignee and its respective successors and assigns all of the Assignors' rights,
titles, interests, and obligations in, to, and under the Registration Rights
Agreement (collectively the "Contract Rights").

         2. ASSUMPTION. The Assignee hereby agrees to assume and perform all
Contract Rights of each Assignor hereby assigned, transferred, and conveyed to
the Assignee and agrees to be bound by the terms of the Registration Rights
Agreement to which the Assignors are a party. Except as expressly set forth in
this Assignment, the Assignee does not hereby assume any other liabilities or
obligations of the Assignors of any nature whatsoever.


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         3. POWER OF ATTORNEY. Each Assignor hereby constitutes and appoints the
Assignee as such Assignor's true and lawful attorney, with full power of
substitution, for it and in its name, place, and stead, but on behalf of and for
the benefit of such Assignee, (a) to demand and receive from time to time any
and all Contract Rights and to get receipts and releases for and in respect of
the same or any part thereof and (b) to do generally all and any such acts and
things in relation thereto as such Assignee shall deem advisable.

         4. FURTHER ASSURANCES. Each Assignor, for itself and its successors and
assigns, hereby covenants and agrees with the Assignee that such Assignor will
do, execute, acknowledge, and deliver, or will cause to be done, executed,
acknowledged, and delivered, all such further acts, conveyances, transfers,
assignments, powers of attorney, and assurances as may be required to assure,
convey, transfer, confirm, and vest unto the Assignee any and all of the
Contract Rights and to aid and assist the Assignee in collecting and reducing
the same to possession.

         5. GOVERNING LAW. This Assignment shall be governed by and construed in
accordance with the laws of the State of New York.


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         IN WITNESS WHEREOF, the undersigned have caused this Agreement to be
signed, all as of the date first written above.

                                        ASSIGNORS:

                                        HM4 TELIGENT QUALIFIED FUND, LLC



                                        By:    /s/ David W. Knickel
                                           ------------------------------------
                                        Name:  David W. Knickel
                                             ----------------------------------
                                        Title: Vice President
                                              ---------------------------------




                                        HM4 TELIGENT PRIVATE FUND, LLC



                                        By:    /s/ David W. Knickel
                                           ------------------------------------
                                        Name:  David W. Knickel
                                             ----------------------------------
                                        Title: Vice President
                                              ---------------------------------





                                        HM PG-IV TELIGENT, LLC



                                        By:    /s/ David W. Knickel
                                           ------------------------------------
                                        Name:  David W. Knickel
                                             ----------------------------------
                                        Title: Vice President
                                              ---------------------------------













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                                        HM 4-SBS TELIGENT COINVESTORS, LLC



                                        By:    /s/ David W. Knickel
                                           ------------------------------------
                                        Name:  David W. Knickel
                                             ----------------------------------
                                        Title: Vice President
                                              ---------------------------------




                                        HM 4-EQ TELIGENT COINVESTORS, LLC



                                        By:    /s/ David W. Knickel
                                           ------------------------------------
                                        Name:  David W. Knickel
                                             ----------------------------------
                                        Title: Vice President
                                              ---------------------------------



                                        ASSIGNEE:

                                        IDT INVESTMENTS INC.



                                        By:   /s/ Howard Millendorf
                                           ------------------------------------
                                        Name: Howard Millendorf
                                             ----------------------------------
                                        Title: President
                                              ---------------------------------