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PCB Construction
The circuit is constructed on a single sided PCB which is designed to fit into the guides in the recommended case. PCB assembly should be carried out following the normal guidelines and recommendations.

There are several wire links which should be fitted first. IC sockets should be used for the IC's as they are static sensitive. Do not fit the IC's into the sockets until all other components have been fitted.

SK1 to SK5 are PCB mounting terminals, and should be fitted with the cable entries towards the edge of the PCB. The LED needs to protrude through a hole in the case, so you may prefer to wait until after the case has been drilled so that you can get the leads the right length.

AWD1 must be fitted with the correct polarity. You may prefer to leave this out until after the circuit has been tested as the noise can become rather irritating (particularly for others). If the relay output is not required, omit RLY1 and R21.

When construction is complete the PCB should be cleaned with a suitable solvent to remove the flux. At this stage it is a good idea to check your work, in particular the soldering.

Assembly
The general layout of the components in the case may be seen from the photographs. Looking from the rear, the alarm sounder is positioned as close as possible to the left to leave sufficient room for the battery to stand beside it.

The sounder is held to the base of the case with two M3 countersunk screws and nuts. Part of one of the PCB guides should be removed so that the sounder sits level. Fitting the sounder will require a pair of long-nosed pliers to hold the nuts - and some patience! A pattern of holes should be drilled in the case in front of the sounder (before the sounder is finally fitted) to let the sound out.

The PCB is fitted in the second set of slots from the top with the components downwards. A 5mm hole is required for the LED. The key-switch may be fitted midway between the PCB and the sounder. On the prototype the phono sockets for the Loop were fitted to the side of the case above the sounder.

Additional holes will be needed for the cables connecting to the remote sensors. The layout of the components within the case is not critical and may be varied to suit individual needs. Check that everything will fit inside as you intend before drilling any holes.

The prototype was attached to the wall by means of two key-hole shaped holes in the rear panel (lid) of the case. The unit can therefore be fitted over two suitable screws once the back is fitted.

Wiring
The interwiring is shown in figure ?. The leads from the alarm sounder will probably be excessively long and may be shortened to suit. Because of the noise, you may prefer to leave this disconnected until after the rest of the unit has been tested.

The battery is connected using a pair of PP9 type battery connections leads, ensuring correct polarity. All other connections are made with 7/0.2mm hook-up wire as shown.

The connections on the key switch can be confusing. In any position the centre contact is connected to the pin towards the back (flat) edge of the key. On the prototype the first (anti-clockwise) and third positions were Off so the relevant tags were not connected. The second position is "Loop & Entry", so the relevant tag is connected to terminal 1 of SK4. The fourth position (fully clockwise) is "Loop Only", and the relevant tag is connected to terminal 2. The centre tag on the switch connects to terminal 3. The two operating positions on the key-switch MUST be separated by an "Off" position to ensure the unit resets correctly when changing mode.

You will also need to make up a lead for the loop cable. This should be made using cheap single core screened cable, fitted with a phono plug at either end. To prevent an intruder from simply unscrewing the covers of the plugs to link out the cable, secure the covers with a small amount of super-glue once the unit and cable have been tested. If a long length is required, it may be more convenient and flexible to make up two or three shorter leads, and join them with in-line connectors having a phono socket at either end.