Originally posted by Arthur P. Bloom:
On a Panasonic and some other systems, the W/Bl pair has dial tone, but not on a Samsung system jack.
That relates to a problem we have over here with some Panasonic systems when people start "playing around" with the connections.
On the BT-style jacks, a regular POTS line is on terminals 2 & 5, with no. 3 of the innermost pair being used as a separate bell feed from a capacitor at the master jack. Some of the proprietary Panasonic systems in their U.K. versions (which don't need the third ringer wire) were designed to use 3 & 4 as the data pair (W/O pair from the PBX). That means you have to determine in advance whether a jack is for S/L or system phone, select the correct type of jack (with or without ringer capacitor) and wire it accordingly.
The average user just sees a phone jack and assumes you can plug anything into it, with the result that some older S/L equipment doesn't ring on incoming calls and/or the ringer bridged from tip to one side of the data pair causes havoc with the keyphones.
Fortunately the later Panasonic systems adopted the scheme they
should have used in the first place, using a 6-way cord and putting the data pair on 1 & 6 of the BT jack. That way all the jacks can be wired the same and accept an S/L phone or keyphone.
But we have added complications with the crossover line cords which are then needed for the proprietary phones, plus there is the added problem two different line cords for S/L equipment to go from the BT jack to the modular on the phone (some putting BT 2/5 to the modular 3/4, others on older equipment using a straight-through arrangement).
You can imagine the chaos that can ensue when users swap cords around without realizing there are different types.
