Is this still a thing?

The telephone line is working, but apparently its health is questionable. We're investigating some other communication methods. If the existing system fails, a neighborhood of homes will lose water.

For my own education, how exactly does this work? ... [diagram below] When the switch closes, it drops the phone line voltage to zero, simulating "off the hook". Is the phone company just programmed to "ring" the base station when the top station line goes off hook? (I get that the ring voltage activates the Wheelock relay.)

Laurel phone ctrl ckt.png
 
Electromatic said:
how exactly does this work?
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That sketch doesn't look right. The Wheelock relay is looking for ring voltage, not -48 DC and one would usually have a double pole relay switching to the line (might also have the -48 floating on the line to make it look connected.

Either way, might as well go for a full telemetry system if installing anything new (actual tank level, intrusion, maybe temperature, power good, etc).

instructions for the relay are at https://www.wheelock-products.com/lanotattachments/download/file/id/466/store/2/crt-t-40i.pdf
 
The Wheelock relay is at the base (lower) station. It is triggered by ring voltage.

The other top station is where there is a tank that needs to tell the lower station when to pump water up to it. The top station is where the 48VDC power supply is. My take is that when the Hand switch or pressure switch closes, it drops the tip/ring voltage to zero, creating an "off hook" signal. I can only guess that the telephone company knows (is programmed) to ring the lower station whenever the top station is off hook.
 
That doesn't make much sense, either. I would expect a dry pair, but if it's an automatic ringing private line I'd expect dry contacts at the sending end which would close to go off-hook. Downside is that this can start the pump but probably not not stop it. (Phone companies seldom want foreign voltage on their lines.)

Could be there's some strange arrangement with the phone company, but it would definitely have been a custom setup.

(For anyone not up on this- ring voltage is floating 90vac 20-30Hz, talk "battery" is filtered -48vdc (earth grounded positive).)
 
WD40 said:
Western Electric' the company that made all the landline gear for AT&T he often bragged even their most basic underground equipment was tested by the military to withstand nuclear fallout so the military could still communicate via land lines deep underground after an attack.
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At that time Western Electric was the major telecom equipment manufacturer in the US. There was Stromberg Carlson and Sylvania/Northern Electric which I think was Canadian, but they were small players. All Bell operating companies which operated systems in most areas used Western Electric equipment. It was over engineered and bullet proof. That was when you couldn't own your own phone, only rent it. When the Bell companies were ordered to divest and end the monopoly in 1984 that ended and any company wanting to manufacture phone equipment was allowed to sell it and connect it to the public network. Gone were the days of "bullet proof" equipment and 99.9999% reliability. It was replaced with whatever made the manufacturer the most profit.

I wonder what Western Electric cell phones would look like.

-Hal
 
Electromatic said:
For my own education, how exactly does this work? ... [diagram below] When the switch closes, it drops the phone line voltage to zero, simulating "off the hook". Is the phone company just programmed to "ring" the base station when the top station line goes off hook? (I get that the ring voltage activates the Wheelock relay.)
Click to expand...
Yes. It's called a ringdown circuit. Old taxi phones in airports and hotels for instance worked that way. If you wanted a taxi, you walked over to a dial-less phone marked "taxi", picked it up and it would ring the taxi company. Hundreds of uses for it. Elevator phones, entry phones, emergency phones, etc.

Not sure, but depending on circumstances it would probably be cheaper than a dry pair because there isn't any special wiring required.

-Hal
 
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