testing telephone cables

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 Question by Teresa Attar posted 02 Jan 1990
 testing telephone cables
Hi, we are having problems with a few of our office phones - they seem to be working but they don't ring. The phones plug into wall ports which lead to patch panels in seperate areas of our office. They, in turn, lead to patch panels in our server room which then plug into the pots unit. Is it just a case of having to check the patch leads for a faulty cable? I've just started internal support and my supervisor has left our employment so I am a bit lost as to where to start troubleshooting. Many thanks, Teresa
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 Answer by Roman Kitaev posted 01 Jan 1990
Hi, Teresa!

If your phones are working, then I think your problem is connected with the so-called "Ringer Equivalence" (RE) overloading.

Each telephone sold in the USA has a ""Ringer Equivalence" number marked somewhere on the phone. The maximum total RE of all connected phones to one POTS telephone line must be less or equal to 5.

If you connect too many phones to one POTS line (ie, the sum of their REs is more than 5), then the phones won't ring because they won't have enough ringing voltage.

Check how many phones are attached to one POTS line and check their RE markings.

For your information, modern phones have RE of 0.25 and 1. Old phones with mechanical ringers have a RE of 1.

Best regards
Roman Kitaev, RCDD

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