an external control unit with a reduced keypad is tightly integrated in a voice activated vehicular telephone system which further includes a voice adapter providing an intelligent interface between the ecu and a portable telephone removably coupled to a portable telephone holder . by taking full advantage of the voice recognition capabilities of the va , the ecu is able to effectively harness the extensive power of the vehicular telephone system while requiring a very small amount of vehicle space through the combination of an internal microphone and a keypad with a very few number of keys . the remaining keys are specifically chosen for their unique value in the integrated system and are further defined to support multiple mode - specific functions . accordingly , use of a voice activated dialer key causes the system during an idle mode to prompt the user to speak a number to be dialed , yet also causes the system during a call - in - process mode to activate a voice - to - tones conversion facility for operating , for example , voice mail systems , without the need for a conventional keypad . likewise , use of a directory key during the idle mode results in a prompt for the user to speak a name previously stored in the directory with an accompanying telephone number for dialing the number , yet use of the same key during the call - in - process mode enables a voice - to - memory conversion facility for storing in scratchpad memory spoken digits which are easily dialed upon completion of the current call .