First microprocessor panels

Microprocessor PCB

All intruder alarm panels at this time were based on ancient mechanical switches, relays, timers for exit and entry periods were set with variable resistors, the “keypad” control was just that, a pad with a few lights and a key. 

There was just one advantage of multiple relay panels, just by looking at the board, you could tell the status of every circuit and that included the alarm circuits, just by the position of the relays, i.e. energised or de-energised.

The microprocessor was invented and available for commercial use in 1973, Chubb were determined to move from mechanical relay switches in their control panels over to computerised control systems, they launched the world’s first solid state microprocessor intruder alarm control panel in 1978, the model CA45.

You would think this technological marvel would be a gamechanger, electronic keypads, digital displays, alarm event memories, programming by keypad commands confirmed on a display, but the panel had none of that. 

What we received looked not much different to the predecessors, the “keypad” was still a mechanical key switch, however now it had several positions, not just on or off. There were a few lights with much the same functions as the previous panel. The main differences were, when you opened the panel, the board did not have any relays, oh and the panel was now painted black instead of battleship grey as had been almost all control equipment for the last thirty years.

An intruder alarm panel has several minimum requirements, a timer for exit period, a timer for entry period, a timer for bell delay to permit police to arrive before intruders are aware they have activated the system, a cut off timer to stop the sounder after a period, an ability to measure an input from each alarm circuit and determine open or closed status. 

This technological marvel had all these abilities, the main connections for detection, sounders and signalling were the same as before, approximately ninety connections along the edge of the board.

Previously these had been screw terminals, but this time they were rows of square pins, the connectors were now Molex plugs and in the bits bag, there was thirty or so two, four and six pin plastic plugs and hundreds of little Molex crimps to be attached to the cables to make up plugs to fit to the panel, engineers now had to crimp the Molex pins to the cables, then insert these into the plugs prior to plugging them into the board. 

We joked that at least this would make changing the circuit boards easy should the need arise. 

The functions of the panel, which zones were part set, and which were full, timers etc, were all set by a matrix of pins soldered into the board, these were numbered from one to ten across, and A to J down, the manual would provide the programming information, connect pin B-4 to pin C-1 for this setting with this delay, in the bits bag for each panel, approximately twenty short black wires with small plugs on each end were provided for programming.

The technology was rolled out with a domestic version, the CA35 and a high security bank style unit, the CA100 which was massive.

Unfortunately, no one had thought of the obvious, a communicator pin interface on the board should have been added and communicators developed to plug on to the interface. 

When fitting signalling communicators previously, they had been connected to the older panels with short wires, tested and then placed back inside their plastic bags and balanced inside the control panel. 

This practice was to continue it seems, and the latest communicators, now with microprocessors on board were rolled out. After a year or so, it came to light that the new communicators were supplied inside black plastic bags, these were anti-static, conductive plastic and caused many issues when they placed short circuits all over the boards that had been wrapped in them for protection, ironically to prevent short circuits.

Many companies followed Chubb and improvements were made with each step, keypads became PIN pads, keys were replaced with codes, text displays started to be normal and some even had real English text two-line eighty-character displays. Programming was by keypad and communicators became plug on. 

However along the way, designers forgot some of the fundamentals of intruder design, crude systems like Rely-A Bell incorporated a fail in alarm state design, the relay was energised all the time, de energising in alarm, or a total power failure, this was replicated in the relay panels which were still in regular use until at least 1984. 

In the early eighties, one company designed an incredibly popular control panel, it seemed to have it all, real English programmable text display, time and date event log, end of line resistor zones connected to expansion modules which in turn were networked back to the panel, plug on communication interface etc. etc. etc.

The main processor, was located on a secondary printed circuit board attached by multiple pin interface to the primary circuit board, this was the panels Achilles heel, an intruder in the know, would force the front entrance door starting the entrance timer, then hit the front of the panel with the palm of their hand as hard as they could, the jolt loosened the pin connections between the processor board and the main board, just a nanosecond power down and a second to reboot, but when it recovered, it was in the day mode, i.e. switched off with no alarm condition.

We were assured that should this knowledge get out, surely intruders would not be aware what control panel was installed prior to breaking in. 

The design even took care of that issue. The setting tone was unique to the panel, starting at a low frequency medium duration pulse on/off tone over a loudspeaker, the tone pulses reduced in length and increased in pitch every two or three pulses until by the time it set.

The noise was intense, loud and very insistent high frequency pulses. 

This could be heard up to fifty meters away, especially whilst the entry door was open, the sound was so unique, it could only be the panel described.

Many companies followed Chubb and improvements were made with each step, keypads became PIN pads, keys were replaced with codes, displays started to be normal and some even had real English text two-line eighty-character displays. Programming was by keypad and communicators became plug on. 

However along the way, designers forgot some of the fundamentals of intruder design, crude systems like Rely-A Bell incorporated fail in alarm design, the relay was energised all the time, de energising in alarm, or a total power failure, this was replicated in the relay panels which were still in regular use until at least 1984. 

One company designed an incredibly popular control panel, it seemed to have it all, real English programmable text display, time and date even log, end of line resistor zones connected to expansion modules which in turn were networked back to the panel, plug on communication interface etc. etc. etc.

The main processor, was located on a secondary printed circuit board attached by multiple pin interface to the primary circuit board, this was the panels Achilles heel, an intruder in the know, would force the front entrance door, starting the entrance timer, then hit the front of the panel with the palm of their hand as hard as they could, the jolt loosened the pin connections between the processor board and the main board, just a nanosecond power down and a second to reboot, but when it recovered, it was in the day mode, i.e. switched off with no alarm condition.

What could possibly be worse, should this knowledge get out, surely intruders would not be aware what control panel was installed prior to breaking in. 

The design even took care of that issue. The setting tone was unique to the panel, starting at a low frequency medium duration pulsing on/off tone over a loudspeaker, the tone pulses reduced in length and increased in pitch every two or three pulses until by the time it stopped, it was intense, loud and very insistent high frequency pulses. 

This could be heard up to fifty meters away, especially whilst the entry door was open, the sound was so unique, it could only be the panel described.