Abstract: An apparatus for indicating to a central service unit of a telephone system having a central service unit coupled to a plurality of station sets whether a particular station set comprises a speakerphone and the type of speakerphone from among two types of speakerphone, is disclosed. The station set includes a microprocessor controller having an input line coupled to a selected one of a low or high logic level. The input line is connected to an electronic switch which receives interrogation signals from the central service unit. Depending on the logic level to which the input line is coupled and the state of the switch, the central service unit can determine whether the station set comprises a speakerphone and the type of speakerphone.

Abstract: A telephone line hold and hold release circuit which, after a central office line which is connected to at least two telephone sets in a telephone terminal system has been seized in response to an incoming call and then placed on HOLD, releases that central office line from the HOLD condition in response to either (i) the re-closing of the hookswitch of the telephone set which seized the central office line, or (ii) the closing of the hookswitch of another telephone set connected to that central office line, or (iii) the release of the central office line by the caller.

Abstract: A three-way power source circuit for portable electronic equipment, such as a radio, is disclosed. The power source circuit comprises a solar energy cell, a rechargeable battery and a standard nonrechargeable dry cell. A transistor couples the solar cell and rechargeable battery to a common point of the circuit, and a second transistor couples a standard dry cell to the common point. The common point provides one of the power output lines to the portable electronic equipment. The solar cell, rechargeable battery and standard dry cell return lines are coupled to a further common point which serves as the return line for power supplied to the portable electronic equipment. Switches are provided for eliminating the flow of current to the portable electronic equipment. The three-way power source circuit allows the solar cell to recharge the rechargeable cell when sufficient light is present.

Abstract: A station interface for a digital electronic telephone switching system is disclosed. The station interface couples a plurality of digital telephone instruments to a digital data bus having PCM encoded signals representative of analog voice signals time-division multiplexed thereon. The station interface enables two way communication between the telephone instruments and the digital data bus and includes a frame store memory for temporarily storing digital data on the data bus and assigning the digital data to system time slots. The output of the frame store memory is selectively supplied under microprocessor control to a digital audio processor which processes the PCM encoded voice signals from the telephone stations and supplies these signals to the audio processor. The audio processor digitally processes both the selected data from the frame store memory and the data from the telephone stations forwarded by a multiplexer, in respective system time slots, under microprocessor control.