Abstract: An office control unit apparatus for transferring digital data between subscriber loops and the time-domain multiplexed communication channels of a multipoint telephone communication network is described. The office control unit receives digital data at its time-domain multiplexed input port and at its loop data input port. In addition to user data, the digital data can include network commands which are processed by the office control unit and acted upon if appropriate. The office control unit is assigned a unique address and can communicate with other network units in response to predefined commands. Data transmitted on the time-domain multiplexed communication channels can be encrypted and the office control unit can process that encrypted data, noting transmission errors and performing majority decision logic where appropriate. Data can be injected into the outgoing data stream at the time-domain multiplexed and loop output ports.