Abstract: After a call is established between two stations using a codec that has been negotiated during call setup, in-band signaling may be used between the two stations to change the codec that is to be used. The in-band signals are indicative that the station that is transmitting the in-band signals can operate with a second codec and are used to probe whether the receiving station can also operate with that second codec. If the receiving station detects and reacts to the in-band signals, then both stations change to communicate with the second codec. The second codec has compatible packet sizes of the deployed (originally negotiated) codec without any need of infrastructure upgrade and/or quality compromise to legacy phone users (i.e., stations that cannot operate with the second codec).

Abstract: After a call is established between two stations using a codec that has been negotiated during call setup, in-band signaling may be used between the two stations to change the codec that is to be used. The in-band signals are indicative that the station that is transmitting the in-band signals can operate with a second codec and are used to probe whether the receiving station can also operate with that second codec. If the receiving station detects and reacts to the in-band signals, then both stations change to communicate with the second codec. The second codec has compatible packet sizes of the deployed (originally negotiated) codec without any need of infrastructure upgrade and/or quality compromise to legacy phone users (i.e., stations that cannot operate with the second codec).

Abstract: A dual-mode telephone has transmit and receive channels suitable for cellular telephony, and is operative in analog and digital modes of communication. Each of the channels has parallel branches of circuitry wherein the circuitry of one branch accommodates voice signals in accordance with an analog protocol and the second branch accommodates voice signals processed by digital compression and expansion circuitry. The digital compression circuitry, which is employed for outgoing voice signals, and the digital expansion circuitry, which is employed for incoming voice signals, constitute a vocoder operative under control of a microcontroller unit. Operation of the vocoder during a digital transmission mode introduces a digitally processed quality to received voice signals, this characteristic being distinguishable from the voice quality of pulse-code modulation employed in the analog communication mode.