Analog Devices

XP 95 Multisensor Detector

The XP Multisensor detector contains an optical smoke sensor and a themistor temperature sensor whose outputs are combined to give the final analogue value.

XP95 Ionisation Smoke Detector

Air in the dual sensing chambers is irradiated to produce ions that travel to the positive and negative electrodes, creating a current flow. As smoke enters the outer chamber the flow drops and voltage increases. The voltage is measured and an analogue signal is converted to digital for transmission to control equipment. Pre-alarm or fire alarm is instigated by the micro-processor when smoke density increases to pre-set levels.

XP95 Optical Smoke Detector

The XP95 optical detector uses an internal pulsing LED and a photo-diode at an obtuse angle. In the event of smoke entering the chamber, the light pulse from the LED will be scattered and registered by the photo-diode. A signal is generated and transmitted digitally using the same method as the ionisation smoke detector above.

XP95 Heat Detector

The XP95 Heat Detector has a low air-flow resistant case for good contact between sensing thermistor and surrounding air. Temperature is measured by a single thermistor network which gives a voltage output proportional to the external air temperature. The signal is processed and transmitted to control equipment.

XP95 Isolator

Isolators are designed to protect the XP95 loop in the event of a short circuit fault. They divide a loop of fire detectors and interfaces into groups of up to 20, so that in the event of a short circuit, no more than 20 devices will be inoperable.

XP95 Manual Call Point

When operated, the manual call point interrupts the polling cycle and can report its address is under 0.2 seconds.

Switch Monitor

Designed to monitor the state of one or more single-pole, volt-free contacts connected on a single pair of cables. Reports open and short-circuit faults on the circuit. The device produces the output states normal, fault, pre-alarm, and alarm.

Three Channel Input/Output Unit

The Three Channel Input/Output Unit provides three voltage-free, single pole, change-over relay outputs and three monitored switch inputs. The unit is designed to supervise one or more normally open switches on each of the three inputs.

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The sensing part of the detector consists of two chambers – an open, outer chamber and a semi-sealed reference chamber within. Mounted in the reference chamber is a low activity radioactive foil of Americium 241 which enables current to fl ow between the inner and outer chambers when the detector is powered up. As smoke enters the detector, it causes a reduction of the current fl ow in the outer chamber and hence an increase in the voltage measured at the junction between the two chambers. The voltage increase is monitored by the electronic circuitry which triggers the detector into the alarm state at a preset threshold. An externally visible LED will light up when the detector changes to alarm state.


Optical smoke detectors incorporate a pulsing LED located in a labyrinth within the housing of the detector. The labyrinth is designed to exclude light from any external source. At an angle to the LED is a photo-diode which normally does not register the column of light emitted by the LED. In the event of smoke from a fi re entering the labyrinth the light pulse from the LED will be scattered and hence registered by the photo-diode. If the photo-diode “sees” smoke on the two following pulses, the detector changes to the alarm state when the indicator LED will light up. The detector housing is identical to that of the ionisation smoke detector. It is distinguished from this type by having an indicator LED which is clear in quiescent state but produces red light in alarm. The optical detectors are easy to disassemble and clean without the necessity of returning them to the factory.


The Series 60 heat detectors are resettable and operate by using a matched pair of thermistors to sense heat. One thermistor is exposed to the ambient temperature, the other is sealed. In normal conditions the two thermistors register similar temperatures, but, on the development of a fi re, the temperature recorded by the exposed thermistor will increase rapidly, resulting in an imbalance of the thermistors and causing the detector to change to the alarm state. Rate of rise detectors are designed to detect a fi re as the temperature increases, but they also have a fi xed upper limit at which the detector will go into alarm if the rate of temperature increase has been too slow to trigger the detection earlier. Fixed heat detectors only change to the alarm state at a preset temperature. Externally, the heat detectors are distinguishable from smoke detectors by having wide openings to the surrounding atmosphere to allow good movement of air around the external thermistor.


The base has been designed to enable detectors to be plugged in without any need for force – particularly useful when fi tting to suspended ceilings. To make it even easier the base has a “one way only” fi t. All Series 60 bases are lockable. The detectors are polarity insensitive and bases are easy to wire with an earth connector. The standard base contains no electronic parts which could be damaged during installation.

Analog Devices