A modular electromechanical key telephone system (KTS) comprising hardwired circuit packs that plugged into a pre-built chassis that included cable connectors for attaching station equipment. Developed by the Bell System and first marketed in 1963, 1A2 systems were an improvement over earlier 1A and 1A1 systems, as they allowed the addition of a limited number of enhanced features through common control cards in the form of circuit packs. Electronic common control (ECC) systems made 1A2 systems obsolete long ago. See also 1A, 1A1, ECC, and KTS.