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Most recent phone won't work in PBX.

Started by Greg G., April 04, 2011, 02:00:34 AM

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Greg G.

This is odd.  When I plug the beige WE 500 I recently got directly into an extension on the PBX, it plays dead.  When I plug it into a 5-way splitter that's plugged into the PBX, it's ok.  I tried it with other phones thinking maybe there's a problem with just that extension (#4), but they all work fine.  I tried it with other extensions on the PBX and it does the same thing.  I don't get why it doesn't like being plugged directly into the PBX, but works fine with being plugged into a splitter that's plugged into the PBX.  ???
The idea that a four-year degree is the only path to worthwhile knowledge is insane.
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GG



Here's the answer, assuming you're talking about a Panasonic PBX:

Panasonic PBXs use the "yellow and black" (or "white/orange pair") for digital communication.  PBXs of the KXTD and KXTDA series can use "digital" phones (KXT-7400, 7600, and DT-300 series) that only need this pair for all of their functions: transmission and signaling. 

PBXs of the KXTA series and older ones such as KXT-616-D and KXT-123211-D, use "hybrid" phones that require a 4-wire circuit.  Speech transmission occurs on the "analog" pair ("red and green" or "white/blue pair"), and signaling (buttons & lights) occurs on the "digital" pair (previous paragraph). 

Your 500 set is doing "something" with the yellow and black wires, and that "something" is probably shorting them together or shorting one or both of them to the red and/or green wires.  This is creating a short between the digital pair and the analog pair in the extension jack from the PBX, which causes the phone to not work.   (Another possible symptom of this is a buzzing or repetitive clicking in the receiver.)

=====

How to fix it:  Open up the phone and look for the yellow (and black, if provided) wire(s).  Then follow the instructions under (1) *or* (2) below: 

1)  If you have a 3-conductor line cord, you can do this:  Leave the yellow wire on the G terminal, but move the black wire of the ringer from the G terminal to the L1 terminal to enable the phone to ring.  The G terminal is completely isolated from anything else, so as long as the yellow wire of the line cord is the only thing connected to it, it won't cause trouble with the PBX. 

If you have a 4-conductor line cord, you also have the black wire to deal with.  In theory you could move all the wires from L1 over to F, thereby leaving L1 blank such that you could screw down the black wire to L1.  However IMHO that's unnecessary and excessive.  Instead, get a piece of flexible plastic tubing of appropriate size, and insert the spade lug from the black wire.  Or just use black electrical tape over the spade lug to insulate it.  In any case put the isolated black wire down into the space alongside the network block, where it will remain in place when the housing is screwed back on.   

-- or --

2)  If the phone has an oldschool 4-prong plug, you may find that the yellow wire is on the Y terminal in the plug.  In that case, instead of doing the above steps, move the yellow wire over to the G terminal along with the green wire, leaving the Y and B terminals free of any wires from the line cord.

If you have a 4-prong plug and a 4-conductor line cord, you may also find that the black wire is screwed down to the B terminal in the plug.  In that case make sure the yellow wire is on the G terminal with the green wire, and move the black wire to the R terminal along with the red wire, and then inside the phone move the black wire to the L2 terminal along with the red wire.   

Note, on AE phones, normal wiring has the yellow wire connected with the red wire, rather than with the green wire.  On SC 1500 series phones, you may find them either way. 

=====

Fortunately, Panasonic PBXs are well protected internally against this kind of thing causing any damage.  Once you fix the phone, the extension jack will work normally for both digital or hybrid phones, and for analog phones.  (On KXTD and KXTDA switches, you can run both a digital phone and an analog phone on a hybrid port; on KXT and KXTA switches, if you use a hybrid phone on a given port, you can't run an analog phone off that port at the same time.)   (Also, always be aware of ringer impedance issues.  Generally it's good to limit yourself to REN 1, or 2 at most, per each extension port.  If too many ringers are connected to a port, phones will ring weakly or not ring on that port.)

Greg G.

Quote from: GG on April 04, 2011, 06:35:37 AM

How to fix it:  Open up the phone and look for the yellow (and black, if provided) wire(s).  Then follow the instructions under (1) *or* (2) below:  

1)  If you have a 4-conductor line cord, you also have the black wire to deal with.  In theory you could move all the wires from L1 over to F, thereby leaving L1 blank such that you could screw down the black wire to L1.  However IMHO that's unnecessary and excessive.  Instead, get a piece of flexible plastic tubing of appropriate size, and insert the spade lug from the black wire.  Or just use black electrical tape over the spade lug to insulate it.  In any case put the isolated black wire down into the space alongside the network block, where it will remain in place when the housing is screwed back on.  


That worked.  It was a 4-conductor line cord with a modular end.  I removed the black wire and wrapped it in electrical tape.

Quote from: GG on April 04, 2011, 06:35:37 AM

(Also, always be aware of ringer impedance issues.  Generally it's good to limit yourself to REN 1, or 2 at most, per each extension port.  If too many ringers are connected to a port, phones will ring weakly or not ring on that port.)


I mostly have only one phone per extension, and only use 3 of the extensions (out of 8 on a Panasonic 308).  The 5-way splitter only has one in-service phone plugged into it.  I use one of the other outlets only when I'm testing a phone simply because it's easier to reach than the PBX.
The idea that a four-year degree is the only path to worthwhile knowledge is insane.
- Mike Row
e