Lamp display for time multiplexed communications networks - e.g. telephone exchanges displays subscriber engaged signals centrally using matrix decoder

摘要

A matrix driven lamp array is presented for use in time multiplexed communication systems for the purpose of indicating whether or not particular subscribers are free or engaged, on a central panel. The subscribers on a particular line each have an address, which is polled during the multiplexing process. Each address is -AND-gated at the polling instant with the engaged or free signal on that line, and the output of this charges up a capacitor at the input to a linear amplifier. The particular amplifier is again chosen by means of an address decoder, so that for a number of subscribers on a particular line, a matrix of capacitors and linear amplifiers is constructed, one set for each subscriber. The linear amplifier drives a lamp during the discharge period of the capacitor, which is arranged to exceed the time taken to poll the entire system. By this means a subscriber's lamp will be constantly lit as long as he is engaged, but will be extinguished shortly after he becomes free.