Television network switching at the post office tower in london

Television network switching equipment is concerned principally with setting up vision and sound routes between various sources and destinations. Due to the growth of the network system this equipment has developed from the simplicity of patch-panels to a complexity requiring a certain amount of automation. In the equipment recently installed at the Post Office Tower in London and also in three provincial centres, provision is made for storing two patterns of connections and their switching times. Pre-setting of information is carried out manually but the actual switching operations are under the control of a clock system driven by pulses derived from the speakingclock TIM. Provision is made for overriding the clock or changing the stored information when last-minute schedule changes occur. The equipment is designed for 625-line colour operation.