A common control for a community office (C.O.) switching system includes two interactive processors. One of these interactive processors is a call control processor which comprises the uppermost element in the control hierarchy. It is a stored program processor and its functions include: (i) control of call progression, (ii) marking paths through the matrix switch network, and translations. The other of these interactive processors is a port event processor. It is a construction of electronic logic circuitry known as "combinatorial logic". The port event processor operates on the principle of the combinatorial logic being sequentially coupled to every one of the port equipment positions over a 4 millisecond scan cycle. A pair of functional units of the port event processor provide the common control capability to sense or transmit supervisory events. These function units also interact with the call control processor in a way which permits the latter to function as the uppermost hierarchical element of the common control with substantially no burden of performing real-time tasks connected with port events. The interaction between the call control processor and the port event processor is effected through a port data store which provides an individual port data field per port equipment position. In general, each port data field is accessible to either of the interactive processors.