20. A non-transitory computer-readable medium comprising instructions which when executed by a processor cause the processor to: receive text that has been entered by a user of a mobile communications device, wherein said text is received when said mobile communications device has been set to a first mode in which said mobile communications device accepts text input instead of speech input, wherein said text is received during a call in which a second communications device is configured to receive speech packets, and wherein said mobile communications device is settable to a second mode in which said mobile communications device accepts speech input instead of text input; convert the received text to a synthesized speech signal; encode the synthesized speech signal to produce a plurality of corresponding speech packets; transmit the plurality of corresponding speech packets over a wireless communications link to said second communications device; and transmit an audio notification informing said second communications device that speech from said mobile communications device following said audio notification will be converted from text, wherein said audio notification is transmitted prior to transmitting said plurality of corresponding speech packets, and wherein said converting the received text to the synthesized speech signal includes using stored characteristics of the user's voice to produce the synthesized speech signal.
20. A non-transitory computer-readable medium comprising instructions which when executed by a processor cause the processor to: receive text that has been entered by a user of a mobile communications device, wherein said text is received when said mobile communications device has been set to a first mode in which said mobile communications device accepts text input instead of speech input, wherein said text is received during a call in which a second communications device is configured to receive speech packets, and wherein said mobile communications device is settable to a second mode in which said mobile communications device accepts speech input instead of text input; convert the received text to a synthesized speech signal; encode the synthesized speech signal to produce a plurality of corresponding speech packets; transmit the plurality of corresponding speech packets over a wireless communications link to said second communications device; and transmit an audio notification informing said second communications device that speech from said mobile communications device following said audio notification will be converted from text, wherein said audio notification is transmitted prior to transmitting said plurality of corresponding speech packets, and wherein said converting the received text to the synthesized speech signal includes using stored characteristics of the user's voice to produce the synthesized speech signal. 23. The medium according to claim 20 , wherein said transmitting comprises transmitting the plurality of corresponding speech packets over the wireless communications link via a transceiver, and wherein said medium includes instructions which when executed by the processor cause the processor to receive said text via the transceiver.