Keeping Burglars At Bay… A Race Against Time!

Member: Sideband

Another example of how a major manufacturer went out of their way to help their customers

During the 70’s Philips manufactured a whole host of products including office equipment and security. Most of the office equipment went through to the main workshop where there was a special area consisting of three engineers.
Burglar alarms were classed as ‘priority’ and came through to the first-line workshop. The purpose of the first-line workshop has been explained in a previous article.

During one of my turns in first-line, a customer who owned a wine warehouse down the road, brought in his burglar alarm that just flatly refused to work. Now some six months previously, I had done a training course on these and repaired a couple since. The expert on these was on holiday so it fell on me to try and sort it out (since I was the only other person to have been involved with them).

The burglar alarms were very simple by today’s standards and worked on the ultrasonic ‘doppler’ effect. In other words they were just a proximity detector. The main box was about eight inches long by about three high and had an ultrasonic transducer at each end….a ‘sender’ and a receiver. There were also six code buttons so you could put in a six-digit code for activation. There was nothing electronic about this, they were just ordinary single-pole push-button switches connected in parallel and pressing any one of these effectively turned the alarm on. However it was knowing how many were turned on and what numbers they were in order to turn it off. If you didn’t know the code, you couldn’t turn it off. (There was a way to find out which we’ll come to next).

The recalcitrant burglar alarm was now sitting on my bench. First thing I did was remove the top and look at the switch unit. Four flags were showing corresponding to the pressed switches which I now pressed. Now no flags were showing so the alarm was off. I’ll explain. When any of the code switches were pressed, a corresponding ‘flag’ showed behind the switch. This was completely invisible to anyone using the alarm and could only be seen by removal of the top cover that had special locking screws. So an engineer could clear any code switches that were pressed.

Now I could work on the alarm. The customer was absolutely correct about it not working. However it wasn’t completely dead and by shorting various test points it was possible to check various parts of the circuit. I nearly deafened myself when I checked the screecher having forgotten to disable the relay. Anyway it proved that the main circuits were all in order so it pointed to one of the main transducers being faulty. They were both the same and all you needed to do was connect a scope across them. The sender transducer was the easiest as it was fed with a constant signal. It was present. However there was nothing across the receiver transducer even when pointing the alarm at the wall immediately behind the bench. So nothing more than a duff transducer then. The service policy was to change both. I didn’t have any in my personal stock so wandered over to the other bench where these were normally repaired. None there either! Into the front spares counter…not stocked in there so it would be an order to the main spares warehouse behind the workshop. As it was a nice day, I wrote the part number down on the job docket and wandered over to the spares warehouse. With urgent jobs, it was sometimes quicker to do this rather than use the conventional method.

Pat the picker’s job was to pick the spares from the racks and send them over to the workshop or front counter. She looked at the number and disappeared into the depths of the stores. She emerged a few moments later saying ‘Sorry we’re out of stock. New lot due in on Friday’. ‘But this is urgent for a burglar alarm’. ‘Hmm, hang on; let’s see if they have any over at North London’. A phone-call later she nodded and said, ‘They’ve got stock over there. Do you really need it today?’ ‘Yes as he has no other burglar alarm’. ‘OK’. Back to the phone she said ‘Can you send a couple over straight away? It’s very urgent’. A further pause and then ‘Be here by about 4pm. Is that OK?’ ‘It will have to be’. Another short conversation on the phone and she said ’They are sending a courier over with them’. ‘Lets hope he doesn’t get stuck in traffic’ I said as I made my way back to the workshop. It was just after lunchtime so there were two and a half hours at least before I could hope to complete the burglar alarm.

Back in the workshop, I told Pete at the shop counter and he rang the customer. If the spares arrived by 4pm, there would be plenty of time as the shop closed at 5pm and the workshop at 5:15. Nothing else to do but put the alarm to one side and get on with other jobs.
It’s now 4:30 and no sign of the spares, the customer is getting edgy as he’s ringing every ten minutes, fearing that he will either have to close without his burglar alarm or stay at his premises overnight. I have the alarm on the bench all ready to work on, all I need are the spares…

Just as I’m thinking that this is one that won’t get finished, I get a call from Pete to say that the spares have arrived. It’s 4:40pm. I rushed out into the shop to see a panting courier driver holding a package. ‘ Flamin’ traffic’, he said. I’ve left the van up the road and run down here before you closed’! He sat down with a coffee and I took the spares from him. Back in the workshop I set about changing the transducers. Fortunately they just plugged in and soon both were changed. A very quick scope check showed that both transducers were now working. I made sure that all the code switches were off, fitted the top and took it back into the front shop just as the customer called in. He had been informed that the spares had arrived and wanted to collect it before the shop closed. He was happy, paid by cheque and off he went.

Leaving the workshop you had to go past security and as I went through the gate, the security guard said ‘I’ve got something for you’ and handed me a bottle of wine. It was from the customer who had checked the alarm and found it to be perfect. Result!! Those were the days!

As a footnote to this story, a few months later a new policy was implemented regarding the service of burglar alarms. It was decided that we would carry a small stock of complete alarms and operate an exchange service. This meant that if a faulty alarm was brought in, a good replacement was given to the customer and the faulty alarm was serviced and put back into stock. Each faulty alarm was serviced to high standards including replacement of any broken or badly scratched casing.

This system worked extremly well and it meant that staff in the front shop could just replace a faulty alarm with a good one to the customer and pass the faulty one through to first-line for refurbishment.