# Determine 4p4c wiring

I tried to make this as thorough as possible. I have a 4p4c socket + cable here. As there is no manual for german wiring I had to measure each wire against each other wire while hearing the "ready to dial" tone to find it out, but I am still clueless.

This is what I got

• 12--0.4V-DC
• 13--4.2V-DC
• 14--0.2V-DC
• 21-0.37V-DC
• 23-0V-AC
• 24-0.1V-DC
• 31-0.4V-DC
• 32-0.001V-DC
• 34-0.2V-DC
• 41-0.2V-DC
• 42-0V-DC
• 43--0.2V-DC

Explaination:

• 1 means white
• 2 green
• 3 yellow
• 4 brown
• First number is one of the colors I put the mass of my oscilloscope to.
• Second number is the color/wire I put the signal of my oscilloscope to.
• one "-" is meant for separation
• Then the value follows
• Then the unit follows
• one "-" is meant for separation
• then there is the type of voltage/current measured

So for instance

43--192mV-DC

means

GND to brown, signal to yellow, result: -192mV, type of voltage/current measured: DC


or

42-5.7mv-AC

means

GND to brown, signal to green, result: 5.7mV, type of voltage/current measured: AC


Please tell me, which cable go to speaker and which to microphone. Also, do I need additional circuitry? In the english wikipedia there is a 500 ohms resistor. Do I need this, what is it for and where to put it?

UPDATE:

On rereading it's not obvious where you are connecting this or what it is you are connecting.

If this is a headset cord (as it seems to be) then what I said about voltages is wrong.

What are you connecting to what?

OLDER:

Nothing makes sense.

If this is to a "central Office" you should have 50V DC somewhere.
If to a PBX possibly 25 VDC or lower.

1,3 = 4.2V and 3,1 = 395 mV suggests that you are grounding the signal with your scope ground in the second case. You need a differential probe or isolated scope or measurements relative to ground.

Connecting ground to one wire will unbalance a feed circuit and allow induced noise from all over. Balanced load or feed must be used.

Use a magnetic earpiece of around 1000 Ohms or a high impedance one with a say 470 Ohm resistor across it. Connect to 2 wires at a time and listen for dial tone. Go from there.

• Thanks. I am going to try kalshagar.wikispaces.com/Cisco+IP+phone+headphone which I just found. – Zurechtweiser Oct 10 '12 at 1:01
• "What are you connecting to what?" I am connecting a telephone cord to a telephone which in turn is connected to my telephone provider. I am picking up the phone so I get the "ready to dial"-tone but of course I cannot hear that because I connected my own handset cord to it of which the ending is being cut so I get the bare wires. There I measured the voltages with an oscilloscope and chose AC or DC based on what made sense. BTW: How can I be notified if someone replies here? – Zurechtweiser Oct 10 '12 at 3:08
• I found kalshagar.wikispaces.com/Cisco+IP+phone+headphone to not be true. – Zurechtweiser Oct 10 '12 at 4:57