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Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
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Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
what is it?
- Thread starter 59frite
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Hey guys, I did a search for diy vacuum car alarm the other day and found a site that was written by somebody that I thought might be able to identify the device. I sent a link to this <span style="font-style: italic">what is it?</span> thread to Ron, the author of Car Alarm Immobilizer and this was his reply to me:
<span style="color: #3366FF">The most sensible place to start - is with the words of the man who built the device. If the device is not disabled then - after a couple of minutes - the electrics are shut down.
I think Nelson is on the right track. I suspect that the glass tube contains some sort of thermal delay - like a thermostat with a built-in heater. When it reaches the right temperature - the thermostat's contacts will open and/or close.
The contacts may be switching the electrical supply directly. But I think it's more likely that they're controlling a relay. And the relay contacts are actually switching the power.
I can see two valve sockets - but I'm not certain what's in the second one. I've seen many different devices plugged into valve sockets - not just valves. They were a convenient way of mounting items - back in the days when there were no PCBs - and everything was attached to a metal chassis.
I think there may be a relay in the far socket. I can't see much of it. But what I can see - looks like a corroded aluminium case. I could be wrong though. Perhaps the two items are identical.
If that is the case you have to ask - "Why are there two? It could be for backup. At a time when components weren't as reliable as they are today - having a second backup device would make sense - especially to someone in the aviation industry.
Another possible reason is that a single device didn't provide a long enough delay. Using two - you could double the length of the delay. You have the initial delay - while the first device heats up. Then it delivers power to the second device. And when the second device heats up - it shuts down the power.
There aren't too many external components visible. There's a tan object below the second valve socket. It looks like a small capacitor - or thermistor. It may be connected to the switching contacts - to help reduce ware. I can only see three resistors. There's one with blue wires - on the left. And there are two more - mounted on pillars - below the board. There may be more under there.
The resistors are probably controlling the amount of current that flows through the heater / heaters. This may be necessary because the devices are not suitable for direct connection to the 12v supply. Or it could be that - by reducing the heater current - you can increases the delay. With a lower current - it would take them a bit longer to warm up.
</span>
<span style="color: #3366FF">The most sensible place to start - is with the words of the man who built the device. If the device is not disabled then - after a couple of minutes - the electrics are shut down.
I think Nelson is on the right track. I suspect that the glass tube contains some sort of thermal delay - like a thermostat with a built-in heater. When it reaches the right temperature - the thermostat's contacts will open and/or close.
The contacts may be switching the electrical supply directly. But I think it's more likely that they're controlling a relay. And the relay contacts are actually switching the power.
I can see two valve sockets - but I'm not certain what's in the second one. I've seen many different devices plugged into valve sockets - not just valves. They were a convenient way of mounting items - back in the days when there were no PCBs - and everything was attached to a metal chassis.
I think there may be a relay in the far socket. I can't see much of it. But what I can see - looks like a corroded aluminium case. I could be wrong though. Perhaps the two items are identical.
If that is the case you have to ask - "Why are there two? It could be for backup. At a time when components weren't as reliable as they are today - having a second backup device would make sense - especially to someone in the aviation industry.
Another possible reason is that a single device didn't provide a long enough delay. Using two - you could double the length of the delay. You have the initial delay - while the first device heats up. Then it delivers power to the second device. And when the second device heats up - it shuts down the power.
There aren't too many external components visible. There's a tan object below the second valve socket. It looks like a small capacitor - or thermistor. It may be connected to the switching contacts - to help reduce ware. I can only see three resistors. There's one with blue wires - on the left. And there are two more - mounted on pillars - below the board. There may be more under there.
The resistors are probably controlling the amount of current that flows through the heater / heaters. This may be necessary because the devices are not suitable for direct connection to the 12v supply. Or it could be that - by reducing the heater current - you can increases the delay. With a lower current - it would take them a bit longer to warm up.
</span>
hey thanks. i appreciate all the feedback. i bookmarked that webpage and will print it out for reference.
as a footnote, i talked to my bro about it and it seems pop did not make it himself but a friend of his (rod bean) gave it to him. some of you might remember he was a hotfootspridget racer back when it was called slolem (sp?) in the days before it became autocross. i guess many of the modifications to this car were made at his suggestion. -just a little trivia there-
thanks again
chris
as a footnote, i talked to my bro about it and it seems pop did not make it himself but a friend of his (rod bean) gave it to him. some of you might remember he was a hotfootspridget racer back when it was called slolem (sp?) in the days before it became autocross. i guess many of the modifications to this car were made at his suggestion. -just a little trivia there-
thanks again
chris