The New Ksion uJ Light Microscopy

A theft communication system is particularly useful for indicating the unauthorized disconnection of a television set or the like from any one of the rooms of a hotel or motel. The communication system includes a central transmitter connected with a master television antenna system for transmitting successive querying scan pulses to sensors located on the antenna line at the location of each television set. Each of the sensors is adapted to apply a reply signal to the antenna line if its sensing circuitry indicates that its associated television set has been disconnected therefrom. The time of reply of each of the sensors is different from that of any other, and the system further includes a receiver connected to the antenna line at a central location for receipt of such reply signals. Such receiver is synchronized with the transmitter so that it can distinguish between reply signals from different ones of the sensors, and is adapted to generate an alarm signal if and only if a sensor replies to two successive querying signals, thereby making the generation of a false alarm due to the appearance of noise on the antenna line as a reply signal exceedingly unlikely.