12" round clock black, surface mount, 110V. Valcom?s state-of-the-art analog clocks incorporate multi-function software, which allows the customer to select communication protocols in the field. This feature provides significant flexibility. The microprocessor-based movement allows you to select anything from a basic sync-wire protocol to a technologically advanced 2-wire digital communication protocol. The clocks incorporate our Valcom 2-wire digital communication protocol, which transmits a stream of data, which constantly checks and corrects every clock in the system, thus guaranteeing that the clocks will never deviate from each other. This data streaming technique makes it possible to mix power and communication signals on the same two wires, thus providing for immediate time correction without replacing existing wiring.