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Author Topic: Connecting a Phone Patch to the phone line  (Read 1726 times)
K4SC
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Posts: 26




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« on: September 22, 2010, 10:32:33 AM »

In the spirit of being prepared to be of aid to someone in a disaster, I purchased an old Heathkit Phone Patch.  Phone Patches used to be as common as dirt, but now seem to be rarely used.  I think having one in any station would be an asset.

My questions revolves around the proper telephone interface device which the instruction manual states as a requirement for use between the phone line and the phone patch proper.  What exactly is this interface?  I suspect it is most likely a simple isolation transformer, designed to keep the amateur from superimposing DC voltages onto the phone line in order to protect the repairman and equipment.  I would have thought the phone patch would contain an isolation transformer to keep the phone companies ringer voltages out of the ham equipment.  Huh  But the manual was quite clear about the requirement for such a device.

I did a Google search and came up dry.  Can anyone who has used a phone patch in the past, describe this device and possible where to obtain one?
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AA4PB
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« Reply #1 on: September 22, 2010, 11:07:16 AM »

Some time ago the interface was required (and provided by) the phone company in order to "protect" their lines. It had zener diodes across the line so that you couldn't put too much audio level in and cause cross-talk between circuits. I found that they often didn't let you put enough audio on the line to get a decent volume on the other end. Most of us just hooked the phone patch across the line without the interface.

It all resulted from the Carter-Phone case were the phone company tried to prevent some company from attaching to their lines. Prior to that I always found the phone company to be very cooperative with hams and their directly connected phone patches. The court ruled that they couldn't prevent someone from connecting to the lines, but they could force them to use a protective interface provided by the phone company. So, we were all supposed to use the interface.

The interface is no longer required or available.
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K4SC
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« Reply #2 on: September 22, 2010, 11:23:31 AM »

Thanks for the information.  When you say it is no longer required, what caused it to change?  I don't want to knowingly hook it up against regulations (FCC?)
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K0BG
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« Reply #3 on: September 22, 2010, 01:06:31 PM »

What Bob told you was correct. I can assure you, that you won't have any problems hooking the Heathkit to the telephone lines. Mine doesn't!
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