Author Topic: What is this??  (Read 1211 times)

Offline Bartonpipes

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What is this??
« on: February 14, 2015, 04:19:30 PM »
First of all I don't know if this is the right place to post this just because of the nature of the question....

I bought a box of miscellaneous phone "junk" today, and I got two of what ever these units are. Can anyone tell me what these were used for, who made them, and possibly what voltage they operate on?

They both have a 4 1/4" long  by 1 1/2" wide black metal cover marked 206-C on the top.

Let me apologize for the bad pictures, I only have a desk lamp and an Ipod touch to work with, but hopefully someone out there will know what this is at a glance.
-Andrew

Offline Bartonpipes

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Re: What is this??
« Reply #1 on: February 14, 2015, 06:23:26 PM »
I found a picture of  a very similar device on a  site about telegraph equipment.

http://www.prc68.com/I/Telegraph.shtml

Apparently it's called a polar relay, but how does it tie in with telephones?
-Andrew

Offline Weco355aman

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Re: What is this??
« Reply #2 on: February 14, 2015, 08:42:36 PM »
It does not have direct connection to a phone. Polar relay's are used in trunk's (between city's) or circuit's that need to detect changes of polarity +/-  or currant flow. They were used in ALL types of switching systems before today's digital systems.
Other than a person with old time switching system they have little use or value.
Phil

Offline Rokumoncat

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Re: What is this??
« Reply #3 on: April 10, 2015, 02:20:10 PM »
Polar relays were also heavily used in Teletype circuits and transmission. A Teletype transmits information using an on off digital signal that is generated mechanically inside of the Teletype unit. They generally used a 5 bit code known as Baudot. For Teletypes that are physically close to each other, a simple loop and current supply is all that is needed. However, if they are a long distance apart, and the signal needs to be transmitted over outside plant via cable or open wire, the on/off signal will quickly degrade with distance and become unreadable without numerous repeaters. In this case, a Polar relay would be used to convert the on-off signal to a +/- signal which will maintain its waveform shape much better than an on-off wave shape would. At the receiving end, another polar relay would be used to regenerate an on-off signal from the polarity reversing signal for the receiving Teletype.

Hope this helps...

Joe