Abstract: An electrical circuit for the control of a parameter of sound, lighting, etc. within an auditorium by a selected one of a plurality of interconnected controlling devices, wherein each of the devices comprises a manual control (R4) for said parameter which is effective upon operation of a latched trigger (G3, G4), the trigger being activated whenever a signal is received from a selection circuit (STROBE) common to all of the devices while a manual switch (SW1) at a selected device is operated, and the trigger becoming unlatched when a subsequent signal is received and the manual switch is not operated.