Candlestick Disassembly

[jarwulf]

I am taking apart a candlestick style 70s phone I have. Beginner so I need to ask a few questions to get my bearing.




Here we have a picture of the dial. I suppose the dial sends pulses that are
interpreted as numbers? Why exactly are there 4 wires from this dial?


Here we have a pic of wires leading to the microphone portion othe
candlestick I assume one of these wires is for power and the other is
for voice data?



What is the purpose of this mechanism above the dial? In the picture
before the receiver handle pushes down the white block you see near
the microphone wires and I guess seems to push on the spring. Is this
somehow disconnecting some circuit?



what is the purpose of this box with all the wires attached to it? Some pulse to tone converter?
I assume the socket on the left is probably for the receiver and the
socket on teh right is for the phone jack? Above I guess is the bell
and I suppose its run by the box to the right of it?

I am interested in identifying the wires I can use to connect the bell, microphone, and speaker/receiver to a microcontroller to control and send and receive data. Is there any way to determine the function of each of the wires? Right now I just have a vague idea based on what they're coming out from. 

[Phonesrfun]

The dial has four wires, 2 to pulse and 2 to mute the receiver while dialing so you don't hear the pulses in the receiver.
The microphone uses two wires in its DC loop.  This is standard for a legacy telephone.  Remember this is an analog circuit.
The mechanism above the dial in the picture is the hookswitch.  It disconnects the line and also mutes the receiver so you don't hear the DC clicks when disconnecting.  There arre several wires involved.
The box with the wires is the telephone network which is found in all phones from the early 50's through the 80's, before electronic circuits were developed.  It contains impedance balancing components of varisistors, and resistors, an induction coil and some capacitors.

What you have is a candlestick look-alike that was a 1970's "modern day" phone designed to look similar to an old candlesick phone from the 1920's.  Yours does not do tone dialing, rotary (pulse) dialing only.

Hope that helps.  I don't know what kind of a minicontroller you are trying to work with.  A standard wiring diagram for a Western Electric model 500 or 702 (Princess) would be the easiest way to get the wiring for this.  They were all very similar.

[Phonesrfun]

This is probably the information for your model.  this is from the TCI document library:

Click on the pdf link below this reply.

[jarwulf]

Looking at the schematic, can anyone tell me if the dial is a normally closed or normally open type?

[poplar1]

Looking at the schematic, can anyone tell me if the dial is a normally closed or normally open type?

Almost all dials have normally closed dial pulsing contacts (indicated by a straight line |). They have to remain closed except during dialing in order to complete the talk circuit. These are the 2 blue wires.

In order to suppress the clicks in the receiver while dialing, the 6U dial in the diagram has two sets of normally open contacts (indicated by an X). Your 6UA dial has one set of normally open contacts--connected to the 2 white wires. In both types, the receiver is muted by shorting it out while dialing.