Abstract: A chess clock is disclosed in which clock pulses derived from a single source are switched alternately and mutually exclusively between two clocks, designated white's clock and black's clock. The mechanism for switching the clock pulses to and from each clock is operationally connected to their electronic circuitry by means of an optical beam, e.g., an infrared beam which is directed alternately to a pair of sensors connected respectively to control circuits for each clock. No mechanical or electrical operational connections are present between the switching mechanism and the electronic circuitry.