Abstract: A 4 KHz channel is used for communication between a processing unit associated with a satellite telephone office and a processing unit associated with a connected class 5 telephone office. A data link circuit is connected to the processing unit of the satellite office and operates to transmit data communications between the processing unit of the satellite office and the class 5 telephone office via the 4 KHz channel.

Abstract: A centrally located digital multiplexer distributes T1 digital signals between a digital central office and a plurality of subscriber service circuits each located at a corresponding subscriber's premises. The subscriber service circuits provide digital signaling and analog line supervision. Analog power supplies and signal generators are connected to the subscriber service units under control of a centrally located microprocessor which communicates with the central office via a dedicated channel in the digital multiplexer.

Abstract: Signals from line circuits requesting service are transferred to a T1 channel via a Pulse Amplitude Modulated (PAM) bus. The number of line circuits which can be served by a T1 line is not limited by the capacity of the T1 line since the probability of all line circuits requesting service at the same time is extremely low. A processing unit detects requests for service and assigns them a slot in a memory which defines the scanning sequence for insertion of line circuit signals in the T1 channel.

Abstract: Common digital line circuits are used in a digital telephone office to provide supervisory and digital conversion functions for any subscriber station connected to a digital telephone office. Subscriber stations are connected to specialized analog line circuitry via an analog access network when required.

Abstract: Pulse Code Modulation (PCM) line circuits include analog and PCM processing circuitry. These circuits are separated into an analog line circuit portion and a PCM processing circuit portion. An analog network is connected to the analog line circuits and provides concentration to a minimal number of PCM processing circuits.

Abstract: A conference arrangement for use in a pulse code modulated system including first and second control memories and a comparison logic circuit. Two words corresponding to two channels are read from information memory during each time slot and after proper comparison, the largest sample is transmitted to a third channel. Also included is a dial tone source for supplying dial tone to all terminations in the system by writing a time slot number assigned to the dial tone source and the respective ones of the channel memory words in the control memory associated with the channels.

Abstract: Switching apparatus is disclosed having a time divided switching network for use in switching time division multiplexed channels employing PCM codes. The network employs two data memories for selectively storing received PCM codes in locations associated with specific transmission channels. These memories are addressed alternately by sequential addressing apparatus and additional memory apparatus which store selected addressing codes. These addressing codes are determined by a control unit to effect shifts in the channel assignments of respective codes by selectively transferring such codes between the data memories, thereby effecting the necessary time divided connections.