Mounting Base

Accepts all Context Plus Xpert card stlyle smoke and heat detectors. It is a zero insertion force base with dual finger receptacles of stainless steel into which the detector terminals slide. Cable connections of up to 2.5mm diameter are made via captive cable clamps.

Includes four double terminals (L1 = – line IN and OUT; L2 = + line IN and OUT; +R = remote LED positive supply; -R = remote LED negative supply) and one isolated single terminal that can be used to provide continuity of an earth or shield. XPERT cards, are supplied with all bases.

Consult the coding guide to determine which pips are to be removed. Pre-printed and pre-punched address cards that save time and increase accuracy during commissioning are available in sets (part number: 45682-127). The base has a ‘one way only’ fit and detectors can be locked into the base by a grub screw with the aid of a 1.5mm hexagonal driver.

20DIsolating Base, XPERT style, 45681-321IMC or 45681-284IMC

The Context Plus XP95 20D isolating base senses and isolates short circuit faults on loops and spurs. The base is loop powered, polarity sensitive and accepts the XPERT card to set the associated device address.

In short circuit conditions, the integral yellow LED is illuminated. The detector associated with the base remains active under short circuit conditions. Power and signals to the affected section are restored automatically when the fault is cleared. Under normal operating conditions, a low impedance is present between the – IN and – OUT terminals of the base, so that power and signals pass to the next base in the line.

If a short circuit or abnormally low impedance occurs, the fall in voltage is sensed and the base isolates the negative supply in the direction of the fault

In applications where it is not necessary to use an isolating base for each detector, up to twenty devices (detectors and interfaces) may be installed between isolating bases, provided that their total switch-on surge current does not exceed 20mA.

Circuits may include spurs, which should be connected between the spare –OUT terminal and the base L1 terminal. Spurs connected in this way appear directly across the loop on the output side of the isolating base. Short-circuit faults on the spur therefore short circuit the loop and vice versa. The effect of such short circuits must be taken into account in the system design and may require the use of extra isolating bases.