Converting phone extension socket to master for PBX extensio

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Hi,

I'm in need of some master phone sockets for use as phone extensions from an analogue PBX.

I have lots of normal phone sockets, can I convert them to masters by simply adding a 1.8 µF capacitor and 470 kΩ resistor in the way shown in the below diagram using these components?

Capacitor - http://www.ebay.co.uk/itm/231069607556

Resistor - http://www.ebay.co.uk/itm/161349300192

a_Phone_wiring_cct_diagram.gif


Many Thanks
 
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Yep, the surge arrestor is not required, known as a PABX master. You will likely get some twits in a bit saying you don't need masters for modern phones. You should still fit masters though, as most standard phones WILL require the ringer.
 
The resistor is not required on PBX use.

Its purpose is to provide a circuit even if no phone is plugged in, for line testing.
 
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All PABX master sockets have the resistor and ring cap. Never seen one with just the cap, never tried it without the resistor, but can see it should work.
 
The rated voltage and capacitor are correct, provided the quality is OK they should b OK, the leads are intended for PCB and may have to be extended.

The resistor may be needed on some PAXs as some modern ones do have line testing functions. But on a PAX unless some of the lines are very long adequate testing can be carried out without the resistor.
 
The resistor is not required on PBX use.

Its purpose is to provide a circuit even if no phone is plugged in, for line testing.
True but it would also provide a discharge path for the capacitor if for example the phone was unplugged whilst phone ringing.
 
The resistor is not required on PBX use.

Its purpose is to provide a circuit even if no phone is plugged in, for line testing.
True but it would also provide a discharge path for the capacitor if for example the phone was unplugged whilst phone ringing.

Good point, I'll add the resistor its not much extra work!

Also I assume + would be too pin 2 and - too pin 3?
 

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