LAST CALL LOG - This feature is available on some speech diallers. It is a log that stores the last telephone number dialled and the last message given.

LATCH - Latch is used when we want to wire back more that one detector to a zone

LCD - Liquid Crystal Display. This is used on two of many keypads. It tends to be preferred by both the engineer and the end user. The keypad offers full 32-character English text display, which is very easy to understand.

LED - Light Emitting Diode. LEDs are used on many control panels, keypads, bell boxes, etc. They are used on the panels as an indication of the function being used. On bell boxes they are used as a visual deterrent.

LIGHT PIPE - This feature is available on some PIRs. It is a clear section at the top of the unit, through which we can see the LED. On a standard PIR the LED is behind the lens, which can be difficult to see when you are a long distance away from the unit.

LOOK DOWN ZONE - This feature is available on some detectors. These units have a lens on the bottom of the detector through which a beam is sent. This gives greater protection by stopping attack from beneath the unit. This is also a useful feature if using PIRs on a stairway.

LOW PROFILE - This phrase is used when referring to bell boxes. A bellbox is regarded as low profile when it is a slim box. This styling tends to be used on domestic applications, as it does not stand out too much.

MAIN USER - This user option is available on a number of control panels. This priority level is able to set, un-set, part-set, test, remove zones and reset after an alarm (if this feature is programmed by the engineer).

MICROPROCESSOR WATCHDOG - The watchdog is there to look after the functions of the microprocessor chip. It is constantly monitoring the chip to ensure there are no problems

MILLIAMPS - There are 1000 milliamps in 1 Amp. Every technology attached to a security system draws current, and this is measured in milliamps, for example: a control panel generally has a 1 Amp power supply built into it, from that we need to deduct the power need for every PIR, Shock sensor, Bell box etc. If we took a basic system in normal mode it would be drawing approx. 550 milli-amps, but in alarm condition this I could jump up to about 900 milli-amps.

MIRROR OPTICS - Mirror optics are used in some detectors, where a concave mirror is used to focus the infra-red energy, rather than a Fresnel lens that is normally used. The advantage of mirror optics is that the infra-red energy is more accurately focused, increasing the quality of detection.

MULTIPLE TRIGGER INHIBIT - This feature is found on a Speech Dialler. It is there to prevent two messages being sent out at the same time.

ONBOARD KEYPAD - This refers to any control panel with a keypad built into it. All programming is done from this point. Depending on the panel being used, one may also be able to use remote keypads as well.

OPEN PCB's - These are lowest specification PCB's available. It is a board with a formal lacquer coating, which gives it some protection from outside extremities, but is definitely not recommended for use at coastal sites, where a high amount of salt air will corrode the unit very quickly.

PAGER + FACILITY - This feature is now available on some Speech Diallers and the Digis. In the event of an alarm condition the units can send a message to a numeric pager

PA OR PANIC ATTACK BUTTON - This is a button that is mounted at easy-to-hand around a house or building, which can be pressed in the event of a person being threatened or attacked. It will generate a full alarm condition, whether the alarm is set or un-set.

PANIC - This zone type is available for use on most control panels. It is recommended that this is used when attaching panic attack buttons to a system. It will generate a full alarm condition, whether the alarm is set or un-set.

PARTITION - Partitions in a panel allow a number of completely separate alarm systems to be controlled from the same panel. This means that, if one partition is inserted in a panel, this will allow two completely separate alarm systems (i.e. separate users, separate, detectors, separate zones, different settings and part sets, etc.) to be run from that panel. This feature tends to be used in applications such as shared accommodation or apartment blocks when one panel can be used for alarm systems in a number of different apartments/premises.

PART SET -This is the mode that will set part of the alarm system, automatically isolating a zone or zones where people may still need to move around. On all panels there are a number part-set suites available, and these can be linked to any number of zones. Part-set tends to be used in situations such as isolating the upstairs of a house at night, to allow people to walk around freely, whilst leaving the perimeter and downstairs areas fully alarmed.

PART SET EXIT TIME - This is very similar to the normal exit time. The part set exit time is the time needed to get from the control panel to your isolated area, when part-setting the system. Again it's a countdown timer; the time programmed by the engineer depends mainly on the agility of the user.

PASSIVE INFRA-RED DETECTOR (PIR) - This is the standard detector used on most systems. PIR detectors are electronic devices that detect an intruder by sensing his body heat when he enters or moves around the area of protection. The device consists of a mirror or lens that can focus the energy, a thermal sensor to detect the energy, and associated electronics to analyze the information.

The mirror/lens divides the area of coverage into multiple zones of detection. This can be visualized by holding your hand out and spreading your fingers. Each finger represents one optic zone of the detector. An actual PIR detector actually uses much more than 5 zones of detection, and some models can detect motion up to 200 feet from the unit. The PIR can only detect motion within one of its zones and is most sensitive to motion across the zones since this is what causes the greatest change in energy.

PERIMETER SYSTEM - Sensing devices that are located on exterior doors and windows that will activated an alarm if triggered.

PET ALLEY LENSES - This is an interchangeable lens available for use with some PIRs. It changes the beam coverage to start the detection at mid room level. This is to allow small pets to walk around under the beams.

PET IMMUNE DETECTOR - There are several so-called "pet immune" detectors on the market. With the ones tested so far, they are pet-immune but only in certain conditions. There is no true pet immune detector yet available, which would disregard an animal no matter what its size or distance away from the PIR. The best way to overcome the problem of pets is to use perimeter protection instead.

PGM - This is a programmable output available on many control panels. It acts like a light switch. If it were programmed for Bell, which would mean that, when the bell box is activated, it would switch on whatever is connected to it, e.g. trigger a relay to activate floodlights or cameras.

PIEZO SOUNDER - The piezo sounder is used on the majority of external sounders. The sounder consists of an electronic piezo element, which gives a very high-pitched output. The benefit of this is that it is low cost and loud, the disadvantage is it is not directional. Police and ambulance sirens also use this type of sounder.

PLAYBACK FACILITY - This feature is available on Speech Diallers. It allows one to listen to the messages recorded onto the unit.

POLYCARBONATE - This is a very strong and resilient plastic that is used for both bell boxes and control panels. It is, to a certain degree, fire resistant as well. To comply with BS4737 regulations, 3mm thick polycarbonate needs to be used.

POTENTIOMETER - A potentiometer is an adjustable resistor which is used for applications such as a volume adjuster on some control panels and a sensitivity adjustment on shock sensors. It has a small wheel that controls the level.

POWER SUPPLY OR PSU - Power supplies are used to give the right voltage and current required to power all technologies on an alarm system. There is normally a power supply built into all of control panels that are 12 volt rated. However, additional PSUs are also sold that are boxed in either polycarbonate or metal enclosures. These tend to be needed for larger systems

PRIORITY LEVELS - These are the differing levels of access given to the users of a control panel. On all panels there is a minimum of Master, User & Set levels available.

PROGRAMMABLE DIAL ATTEMPTS - This feature is used on both the Speech Dialler and the digi. A specified number of dial attempts are programmed into the module to ensure the unit will try a telephone number several times, in case it cannot get through first time.

PT E/E - This zone type is probably one of the most useful zone types available. It is a two in one zone. It acts like an access zone in full set, in that it will allow a person to walk through as long as the entry/exit zone is opened first. In part-set it acts like an entry/exit zone starting the entry timer as soon as it detects a person. It is suitable for use in open plan rooms.

PULSE COUNT - This is available on both some PIRs and shock sensors. Pulse count is incorporated to try and prevent false alarm activations. It will count a number of activations before going into alarm. For example, if a PIR is set at pulse count 3, it would have to see movement in three zones of the detector beam pattern before it would go into alarm.

PYRO - A pyro or pyro element is the thermal sensor that is used in infra-red detectors (PIRs, Quads and Dualtechs)