# Old telephone system



## bull mike (Nov 4, 2014)

Anyone seen an old telephone power board circa 1960


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## bobelectric (Feb 24, 2007)

I think they have a telephone museum in Canton, Ohio.


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## Nom Deplume (Jul 21, 2013)

Is that slate?


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## Big John (May 23, 2010)

So, what was it supposed to do? What's the mystery component inside the heat sink?


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## LGLS (Nov 10, 2007)

In one particular downtown hi-rise in Manhattan, the Telco was making arrangements to run another fiber riser to a tenant that was going to occupy numerous floors. The buiding management company refused to allow to install due to the lack of real estate, as all the Telco risers were occupied by 1200 pair trunk cables and new conduit would have been a freak show considering all the obstacles. The demand was for the Telco to remove ALL outdated and non-functional risers and abandoned equipment within the communications closets and shafts. There was a 6-8 month standoff until the Telco caved. By the end, 3/4 ths of the risers and every punchdown backboard, power supply, was removed. Some of this stuff dated back to the 1930's. Then the Telco wanted to run 1 fiber up EACH RISER, (4") in order to block competitors!


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## mikeh32 (Feb 16, 2009)

yeah, still in use. i will find pics. Still have to solder the connections to it too. 

oh lovely chicago


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## fdew (Mar 26, 2009)

That board was made by IBM It was called a booster It received the pulses that ran there three wire impulse clock system and sent out identical pulses. It would be used in large buildings such as schools or hospitals with one of them in each wing or floor. 

I have serviced a large number of them.


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## 8V71 (Dec 23, 2011)

Big John said:


> So, what was it supposed to do? What's the mystery component inside the heat sink?


That would be a selenium rectifier.


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## bull mike (Nov 4, 2014)

I was unsure of its actual purpose . I just knew it was connected to phone lines . It was still "in use" The facility was multiple buildings. With external & internal phone lines. Thanks fdew for the information. A little history is good


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## fdew (Mar 26, 2009)

If they were going between buildings with phone lines it would make sense to use this because the phone lines would see the current needed to pull in the two relays.

BTW When a selenium rectifier receives 60 hz and has a load on it it will hum slightly. We would use this fact when setting clocks "by hand" We would manual close the relay on the left (A relay) 50 times to move the clocks ahead one hour. Then we would click it a few more times while listening closely until the hum stopped. At that point we knew all the clocks including any that were sluggish were at the same time. (no more current draw. Then we would hold down the right relay (B relay) and click the A relay about 10 times to get the clocks going to the next hour. 

The relays would fail every few years. When they failed with a contact bounce the clocks would scatter. I replaced them with solid state relays.


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## gnuuser (Jan 13, 2013)

Big John said:


> So, what was it supposed to do? What's the mystery component inside the heat sink?


that is a selenium rectifier they have been classed as hazardous and removed from electronics

bullmike do not power that thing up unless its in a well ventilated area 
the fumes are hazardous


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## Abeyta87 (Mar 10, 2013)

I found this a few weeks ago in an old bank.


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