GB1528453A - Alarm systems - Google Patents

Abstract

1528453 Alarm systems TEATHER INTERCONTINENTAL GAS DETECTION (UK) Ltd 10 March 1976 [10 Dec 1974] 53327/74 Heading G4N In an alarm system including a detector and a control panel 2 having at least one alarm relay controllable by the detector and a check alarm potentiometer which is disconnected from the system during normal operation, an interlock arrangement in the panel comprising a manually actuatable cam 5 having two positions, a spring loaded sliding screen 7 mounted for movement by the cam to cover and uncover a plurality of access apertures 4 in said panel to pre-settable controls, and two microswitches 6 operable by the same, the arrangement being such that in a first position of the cam it holds the slide in a position to cover the apertures 4 and in a second position it releases the slide to uncover the apertures and actuates the microswitches, one of which maintains the alarm relay energized to prevent initiation of an alarm signal, and the other of which disconnects the detector from the systems and connects in the check alarm potentiometer. Fig. 1 shows the front and Fig. 2 the back of the panel. The detector may be a gas detector for monitoring a process or equipment, and its output signal is applied to an amplifier and threshold comparators having two reference levels, one alarm relay being de-energized to light one lamp 10 when a first level is exceeded and a second alarm relay being de-energized to light a second lamp 10 when the second level is exceeded. The cam 5 is operable by a keyoperated lock 6 and the slide 7 has apertures which coincide with the apertures 4 in one position of the slide. As described the apertures 4 contain controls for adjusting meter zero MZ, meter setting MS, a recorder RS and reference level settings A1 and A2. A knob 3 adjusts the check alarm potentiometer.