Abstract: A housing (11) which is intended for mounting on a process control valve (5) contains electric circuits (3) and means (4) controlled by these circuits for converting electric control signals into operating signals which operate the valve via a cylinder. The electric control signals are supplied via a serializing terminal (7) from the computer (1) of a process control system which includes a plurality of process control valves (5). The housing has a single interconnection (14) with a cable (8) common to several process control valves for transmitting the control signals and for supplying the electric circuits with power. The housing moreover has a single connecting socket (13) to permit coupling the housing to a pressure air line common to a plurality of valves (5).