The PSC VODEC PA/GA system can be connected to a site Fire and Gas detection system to allow the automatic initiation of alarm tones signal. An automatic alarm inhibit panel can be optionally specified which disables the interface to the external site detection package thereby preventing spurious alarm trigger during, for example, maintenance procedures. The panel comprises of a 19 inch rack mount 1U (44.5 mm) face plate which is equipped with a key operated maintained switch assembly. The key switch status is indicated on management host VX/AT-M and is repeated at master PA/GA access control positions as a further warning that the auto input is disabled. The inhibit key switch contact arrangement is based on a N/O (normally open) “closed to inhibit” auto alarms philosophy and is connected to the host PA/GA system via a 2IP interface port by a single pair of conductors.