atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telephone Repairs & Equipment wiring diagram for a North Supply Co 250044-QBA-27M-CH

Hi, I'm new to this so forgive my misnaming of parts etc. I am currently working with a basic 2500 phone with message waiting light I bought on online. It worked fine, but I am building a new case for it, so part of my project was to disconnect the various components from the main board to build the case.

I was trying to be as careful as possible mapping out the various wire connections to the main board from the various components....but halfway through I found a loose connection that was not taped off previously. It is attached at one end to the Connect/Disconnect mechanism. My guess is that it is a lead to the keypad as there was one there already. This wire is shorter than the others and is grey with no other colours (if that means anything)

If someone here has a wiring diagram for the main board of this model phone so that I can confirm the location of this errant lead that would be very helpful. I've mapped out all the other plug connections from the line in handset and keypad to the main board, just this last lead from the connect disconnect mechanism is left dangling and without a home. Please help!

Welcome.

You need to know the names for the components, so we can converse.

The "connect/disconnect" mechanism is called a hookswitch in non-Bell System language, and a switchhook in Bell language. On certain BSP's (Bell System Practices...the bible of the phone company) it is called a lineswitch.

The other parts are called the network (the thing with all the screws) the ringer, and the dial.

The gray-colored wire is not gray. It is "slate" abbreviated "SL" The abbreviation for gray would be GR which conflicts with GReen, so the color is called slate.

In most industry standard 2500 sets (i.e. those not made after 1990 and/or made in China) there is one extra lead from the switchhook that is not connected to anything. It is a transfer contact from the switchhook that is used for speakerphone service.

If you refer to this diagram,

2500D BSP

you will see the SL lead is stored on terminal L2 of the network. Maybe that's where it goes in your phone.

Most North Supply products in the 25XX family followed ITT design, so try searching this phone's part number as an ITT product for the wiring diagram.

Oh no! I installed a 25 pr cable the other day and the last pair was Purple/Gray!

Thank you for posting the hookswitch/switchhook difference. If you think about it, switchhook makes more sense.

Switch-hook is the part that you hang the receiver on when you are done talking.

Hook-switch is the device that is actuated when you hang the receiver on the hook.

Before the patent on the hook-switch ran out, you had "paddle" phones, where you leaned your elbow on the paddle, which actuated a normally-open switch into the closed position, and connected you. Don't move your elbow, or you're done talking!!

The "hook" part of the name comes from the old oak wall phones. The transmitter was built into the body of the phone while the receiver was hung up on a hook that activated switching contacts built into the phone.

We still say "hang-up" when we disconnect.

BTW - The British say "ring-off" when they disconnect. On the oldest manual exchanges there was no indication for the operator that you had disconnected so you were supposed to crank your magneto (and ring the bell) to let her know you were done.

Sam