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2500MM Wiring help

Started by allnumbedup, October 30, 2021, 12:57:29 PM

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allnumbedup

I have finished this 2500MM. I restored for my elderly father. I added weight to the G6 handset to help him use a phone with his Parkinson's plus hearing loss.  I followed the 2500MM wiring diagram but don't have the note for the ringer wires.  The 2500MM has a hookswitch with has 6 instead of 7 wires and a little different pile of contacts--slate is missing and the color coding is different.  It also uses tip and ring to terminals A and F.  I used an older four wire ringer and found that the slate and slate/red wires needed to be attached for it to ring.  Attaching these two to a 0.47 cap allowed only for a tinkle so I think the internal capcitor in the network is being used between K and A.  I have the extra two ringer wires attached to T2 together as my only free terminal.  Works fully but seems odd and wonder if I have something wrong or could run into a polarity issue when I plug it in-- if his home is reversed and I have to flip tip and ring (the TT is not polarity guarded).  I have not seen a 2500MM before and don't really understand why this wiring scheme was used instead of the 2500DM.  thank you
Analog Phones for a Digital World

Key2871

That ringer wires the same as any 2500 set.
Black ringer to L1 with green line wire.
Red ringer to L2 with red line wire.
Slate to A on the network.
Slate Red to K on the network.
Switching either leads doesn't matter as long as they go to the filter cap.

If it's a different ringer than a C4A ringer post your ringer type and wires available for connection. Then someone can give you the correct information.
KEN

poplar1

2500MM is designed for use with 1A2 Key System. One set of hookswitch contacts (yellow and brown) are designated A and A1. When the phone goes off- hook, it will make the multi-line sets on the same line light up on that line. If the line is put on hold on the multi-line set, the MM set will release the held connection.

Diagram shows a C4B ringer. Strapping the Slate and Slate-red leads together on your C4A makes it electrically equivalent to a C4B.
"C'est pas une restauration, c'est une rénovation."--François Martin.

allnumbedup

#3
I see now how the diagram works with a keyset--using the yellow and black wires in a standard four wire modular cord for the purpose.  I guess if I move the switch hook wiring around I could revert to a std 2500 conncetion of tip and ring as well. Appreciate the ringer explanation,  it is a regular C4A from 1966.  I have never had to connect the slate and slate red together before on a C4A. thank you
Analog Phones for a Digital World

5415551212

Quote from: poplar1 on October 30, 2021, 01:45:51 PM
2500MM is designed for use with 1A2 Key System. One set of hookswitch contacts (yellow and brown) are designated A and A1. When the phone goes off- hook, it will make the multi-line sets on the same line light up on that line. If the line is put on hold on the multi-line set, the MM set will release the held connection.

Diagram shows a C4B ringer. Strapping the Slate and Slate-red leads together on your C4A makes it electrically equivalent to a C4B.

Interesting so on a key system would this be connected to the phone line ahead of the KSU as there would no longer be ringing signal on the line after the card?
Then the A leads connected to the 400x KTU card.


poplar1

Quote from: 5415551212 on October 30, 2021, 02:43:17 PM
Interesting so on a key system would this be connected to the phone line ahead of the KSU as there would no longer be ringing signal on the line after the card?
Then the A leads connected to the 400x KTU card.

There *is* ringing current from the central offce whether before or after the card. Normally, you would connect the set *after* the card, the same as you would the multi-line sets, and use the default wiring of the 2500MM where the ringer is connected to F and K on the network.

This ringing method means the ringer is a "line ringer": the ring will follow the ringing cadence from the central office.

Optionally, you can use a 6-conductor mounting cord (line cord) and connect the ringer to the blue and white leads of the 623D6 modular jack on the basepan. This is for "common audible ringing" from the key system. However, you will also need a diode matrix so that the ringer does *not* ring on the other key lines which are not available on this single line set (phantom ringing).

When used as a single line set without a key system, I usually move the yellow hookswitch lead from G to L1. Otherwise, if there is a second line on the wall jack, or a transformer for a Princess or Trimline, the second line or transformer will be shorted out whenever the 2500MM is off-hook (unless you are using a 2-conductor mounting cord, which may or may not get changed to a 4- or 6-conductor cord by an unsuspecting person later on).


"C'est pas une restauration, c'est une rénovation."--François Martin.

allnumbedup

Sure enough this phone came with a six line modular jack,

good to know about the yellow lead but I did not think to check the other phone after installing this one when this one is off the hook. Now the phone 500 miles away, so maybe next visit to my dad.




Analog Phones for a Digital World

5415551212

Thanks for the great info poplar1
The A leads are a curious thing to me in the key systems, because its pretty easy to detect an 'off hook' condition by other means.
Cheers
--Stephen