I just scanned this, and I really wish I could get my fingers into one of those, I barely remember it from when I was a small boy.
a and b is the regular line. When the excange register off hook the c wire gets negative voltage, related to ground, and keeps it until hang up. When party answers the d wire get a ground pulse, and the coin is collected. If no answer, the coin will be returned on hang up.
dsk
Here is a picture of a refurbed one from the Norwegian Telemuseum.
Interesting that these payphones used 4 wire lines like this. Do you know if this was done to allow calls to the operator and to other "free" numbers without coins, and if not that then why were they set up this way. Also do you know if they required any special equipment in the central office.
This page is all I know, and yes it is stated to be special equipment at the exchange. The dial pulses was shorted until it received a coin, so no free numbers, no police etc.
dsk
Quote from: Kimball321 on January 30, 2017, 12:42:24 AM
Interesting that these payphones used 4 wire lines like this. Do you know if this was done to allow calls to the operator and to other "free" numbers without coins, and if not that then why were they set up this way. Also do you know if they required any special equipment in the central office.
Unfortunately I find Scandinavian languages difficult to decipher but:
- the additional connections are there to supervise coin collection.
- Additional equipment is required at the exchange to collect coins.
- the phone does not make use a common reversal on answer (and if one occurred the phone would not work)
It seems that a local AC power supply is required to sound the "insert coin" buzzer.
If you thought you might make a second call on the one coin by dialling with the hook switch, think again, the hook switch is dampened to prevent it.
dsk, what is the inductor to the left of the dial?
Jack
I have tried to translate it:
dsk