3-wire Phone on a 4-wire network

[Craterranch]

Hello. I'm cleaning up a Western Electric 302 to use at my place of work. The 302 is a 3-wire phone, and the line at work is a 4-wire (I have not yet confirmed whether we actually use all 4-wires). I purchased a pulse/tone converter online, wired it to the phone, and plugged in the work line...I could call to the 302 successfully, but could not call out from it. Thinking I should probably change the attachment points on the converter, but I'm not sure where (it came from China and has no documentation whatsoever). Any thoughts are appreciated.

[unbeldi]

Welcome!

Your 302 phone is actually from Canada and was made by Northern Electric.  Does the handset handle show Western Electric?
Furthermore, the plastic housing is actually not from a 302, but from a mostly empty handset mounting, called AB-1, used to convert old candlesticks phone with magneto ringer boxes to something more modern, but still using the ringer box.  This was called a 251 telephone set.

[correction: what I described was the 250/AA1 telephone, but yours is the 251 which was only missing the ringer when sold to a telephone company]

Of course it is now a 302, someone used the housing on the 302 base with all the electric components present.
Congrats.


You only need two wires to run this phone, red and green. The third wire (yellow), was used for grounded ringing which is long obsolete, not needed.

On a modular jack, you only connect to the middle two contacts, no matter you many pins there are.  They may have wired the office for two lines at each desk.

This device has three connection points.  P1, L1, and L2.  It is not entirely clear where those wires go that disappear under the PCB.

When you called this device with 302 from another line, was the audio fully functional or did you only test ringing?

[Craterranch]

Umbeldi,
Thanks for the info. Yes, incoming calls were fully functional. I did not have the yellow from the phone hooked up, just the green and red as shown in the image.

Under the handset it says Western Electric Company USA FIW.

[poplar1]

Does the phone ring on an incoming call?

Do the office phones have more than one line, as well as a hold button? Or are they single line phones like you'd find in a residence? Do you know what kind of system your office uses?

[Craterranch]

The phone rings on an incoming call and works just as it should in that respect.

The office phones are actually quite retro for a modern office; they look like a 502 but with buttons instead of a rotary. No hold button. Pretty sure they are just single lines (we have call waiting, but there is no way to choose a different line).

[NorthernElectric]

Any thoughts are appreciated.

This thought is either really dumb or totally brilliant.     Did you try dialing 9 for an outside line first? 

[unbeldi]

So what exactly happens when you try calling FROM the phone?

I presume you have dial tone when lifting the handset and listen?

What happens when you turn the dial and when you release it?

[Craterranch]

So what exactly happens when you try calling FROM the phone?

I presume you have dial tone when lifting the handset and listen?

What happens when you turn the dial and when you release it?

There is a dial tone when lifting the handset. Dialing I can hear the pulses and see a light blink with each one on the converter, followed by a tone. But no ringing or connection after that.

[unbeldi]

So what exactly happens when you try calling FROM the phone?

I presume you have dial tone when lifting the handset and listen?

What happens when you turn the dial and when you release it?

There is a dial tone when lifting the handset. Dialing I can hear the pulses and see a light blink with each one on the converter, followed by a tone. But no ringing or connection after that.

Getting dial tone and seeing the pulses on the gizmo is good.  Hearing the pulses is not.  Hearing a tone, I think means the converter is actually recognizing the digits and producing the DTMF signal.  That's good to know too.

Does the dial tone stop after the first digit is dialed?

A correctly wired 302 telephone prevents the user from hearing the dialing through the handset.  The phone is probably miswired internally.  Normally the receiver (ear piece) is electrically disconnected by the dial.

[NorthernElectric]

I found some pictures of this device which suggest that Craterranch has it wired according to the manufacturers directions.



The website (aliexpress), which I assume is marketing this device,  was not much help:

Please note: DIALOR2.0 for electrical demand is on the line


Dc voltage: 32 v, 48 v.Current: 20-40 ma;



Because the DIALOR1.0 is installed with the inside of the telephone module;Need a slight electrical sense can refer to the installation manual installation;For the sake of more and more people like old phone birth DIALOR2.0's installation is very simple;End in line standard joint, the other end connected to the telephone of the 2 wires can!

I did not find a link to the actual product documentation.

[Phonesrfun]

Please note: DIALOR2.0 for electrical demand is on the line


Dc voltage: 32 v, 48 v.Current: 20-40 ma;



Because the DIALOR1.0 is installed with the inside of the telephone module;Need a slight electrical sense can refer to the installation manual installation;For the sake of more and more people like old phone birth DIALOR2.0's installation is very simple;End in line standard joint, the other end connected to the telephone of the 2 wires can!

Perfectly clear. 

[G-Man]

According to the instructions for your Dialor 2.1+, it appears that you have it properly connected. However, the specifications specify it will work on lines delivering 32 to 48-volts @20-40 ma. Some pbx or VoIP lines will only supply 24-volts or less, so that may be the cause of your problem. What brand and type of telephone system does your office use? Is it a large office with a large number of employees and telephones?

[G-Man]

Here is another photo captioned with very explicit instructions.

[unbeldi]

None of the pictures of these units that I have found showed the type of µ-controller used in the design, but I suspect it is either a PIC16 type chip or an Atmega8 or so. The DTMF generator is a Holtek 9200, used very commonly in DTMF applications.  The DTMF chip probably uses more power than the controller chip and should be satisfied with 1 mA or 2. So I cannot see for the world how this board can possibly consume 20 to 40 mA.  On the micro-controllers I have used, I can barely even detect the power consumption with a standard handheld milliamp meter. But with poor programming and driving that LED, I can imagine the board using 10 mA perhaps.

So, I suspect that power specification is actually a loop specification required to operate a phone AND the gadget.

Of course, like in the other recent case we discussed here, the power requirements available on the loop are critical.

This board doesn't seem to have any kind of energy storage capacitor to provide a boost during DTMF generation.

The voltage 'specifications' are also too high, the chips on the board will run fine with less than 5V even.

[unbeldi]

First we need to establish whether the tones that the unit produces are strong enough to break dial tone.

Do you have any other rotary phones to use as alternate test instruments?