Abstract: A voice messaging system is implemented using a PCMCIA card or other type of card, and a host call processing device such as a PBX switch. The card includes a processor operative to implement various voice messaging system functions, and a memory for storing voice data used in the voice messaging system. The host call processing device has a socket adapted to receive the card. The card receives voice data from the host call processing device for storage in the memory, and delivers voice data retrieved from the memory to the host call processing device. The voice data is communicated between the card and the host over a custom serial bus which includes a time-division multiplexed voice data line divided into a plurality of time slots, each of the time slots providing a distinct voice data channel at a designated bit rate.

Abstract: A wired logic PBX switching system is disclosed in which a camp-on circuit is used to provide automated call hold service. A station user places an existing call on hold by flashing the station switchhook contacts and dialing a predetermined code. The dialing of the code disconnects the station from the first call and places the trunk circuit serving the first call on hold. A second call may then be placed from the station. Upon termination of the second call, the hold condition is removed from the trunk circuit and a connection is reestablished from the trunk circuit to the station.