Exhibit B JOINT FILING AGREEMENT The undersigned hereby agree that the Statement on Schedule 13G/A, dated September 9, 2008 with respect to the shares of Common Stock of Inphonic, Inc. and any further amendments thereto executed by each and any of us...

Exhibit B

                             JOINT FILING AGREEMENT

                     The undersigned hereby agree that the Statement on Schedule
         13G/A, dated September 9, 2008 with respect to the shares of Common
         Stock of Inphonic, Inc. and any further amendments thereto executed by
         each and any of us shall be filed on behalf of each of us pursuant to
         and in accordance with the provisions of Rule 13d-1(k)(1) under the
         Securities Exchange Act of 1934, as amended.

                     This Agreement may be executed in separate counterparts,
         each of which shall be deemed an original, but all of which shall
         constitute one and the same instrument.

         Dated: September 9, 2008

                                            POTOMAC CAPITAL MANAGEMENT LLC

                                            By:   /s/ ▇▇▇▇ ▇. ▇▇▇▇▇
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                                                  ▇▇▇▇ ▇. ▇▇▇▇▇, Managing Member

                                            POTOMAC CAPITAL MANAGEMENT INC.

                                            By:   /s/  ▇▇▇▇ ▇. ▇▇▇▇▇
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                                                  ▇▇▇▇ ▇.▇▇▇▇▇, President

                                            ▇▇▇▇ ▇. ▇▇▇▇▇

                                                  By:   /s/ ▇▇▇▇ ▇. ▇▇▇▇▇
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                                                  ▇▇▇▇ ▇. ▇▇▇▇▇