Speech recall in cellular telephone

Abstract

A cellular telephone having transmit and receive channels with a digital-mode communication capability includes also a memory and switching circuitry operative under control of a microcontroller. The switching circuitry enables connection of input and output ports of the memory to either one of the channels. By entry of commands to the microcontroller, the microcontroller arranges the configuration of the switching circuitry to permit storage in the memory of a message originating locally from a user of the telephone, inputted via a microphone connected to the transmit channel, or from a distant telephone connected via a communication link to the receiving channel. Subsequent playback of the message from the memory may be coupled via the switching circuitry to a speaker of the telephone to be heard by a user of the telephone, or may be outputted to the transmit channel for communication to the distant telephone. Preferably, the message is stored in compressed format to save memory space. This enables the telephone to provide features of prompt, voice pad, transcription, and voice mail. In addition, a reduction on a data sampling rate, in response to the condition of a battery charge, permits an extended period of operation of the telephone prior to the termination of adequate battery voltage.