The Single Target Block Signal No. 163 would display either one of the RED or GREEN lamps that were housed behind its single opaque opening as a train approached. This signal used a 153C Contact that would be placed beneath the track and would be activated by the weight of a passing train.

Produced from 1961 until 1969, early versions came an a box whose end is illustrated below. Those signals that were sold in 1969 came in a plain white box with the information stamped in ink on the end.