GPO 706 has dial tone but will not ring on RTX wireless extension

[PaulS69]

Hi! We have recently bought an old working (converted) 706 for a ornamental piece in a new hall way. We have the main BT point (data and phone)  in the lounge where we have a BT cordless base station connected  and also a 70s Trim phone (another working ornamental piece) connected by a 3 way adapter. So I bought an RTX wireless extension on eBay to connect the 706 in the hall which I have connected and appears to work. I have set up as per the instructions with the main phone line going into the base station (from the 3rd port on the 3 way adapter) and connected the 706 In the hallway with the accompanying RTX extension unit. The 706 has a dial tone and will take an incoming call but it will not ring. I know the phone will ring as I have tested it direct into the BT socket. Does anyone have any ideas re how to solve the issue? I read ok another forum about the 706 needing the addition of a capacitor? Any help and/or advice would be great! 

[Keith_Beddoe]

@PaulS69 

Who provides your phone service?

[PaulS69]

BT

[PaulS69]

BT. They recently  fitted a new box as we need to move it owing to building work we had going on. The new box is the “fatter” type. We have BT Infiniti and BT landline 

[Keith_Beddoe · Accepted solution]

The old phones have a mechanical bell and need a good ringing current supply to work properly. They also require a third "bell wire" connection to complete the ringing circuit.

If your wireless extension only has two wires, then you could either fit a master phone socket which would have the capacitor inside, or try plugging in a microfilter into the wireless extension, and plugging the phone into that.

Microfilters have built in capacitors to maintain the ring wire on pin 3.

[iniltous]

Could be something of a problem of the past, made relevant by using ancient equipment,  it could be the ‘REN’ , ring equivalent number, all devices connected to a phone line have a REN, the combined REN of the devices on the line shouldn’t exceed ( as far as I remember ) 4, with more modern equipment , the combined REN is not normally an issue, but a 60’s or 70’s phone with a bell set rather than an electronic ringer , in combination with other devices on the line may exceed the REN maximum.....if the retro phone ‘rings’ when connected with all other devices disconnected, that does suggest it may be the issue.

The ringing current sent to line to all devices irrespective if they are designed to ‘ring’ is relatively small, connect too many devices and the ones designed to ‘ring’ may not respond to the diminished ‘ringing’ current, that’s why there is a REN in the first place

[PaulS69]

That makes sense. So my current set up is an adapter with

the 3 phone ports coming out of the main wall socket. Plugged into the this adapter is the cordless base station that has 3 handsets and the Trim phone. All ring when calls come in. When I connect the RTX wireless extension the 706 does  it ring  but has a dial tone. I unplugged the cordless base to see if that made a difference and it did not, so I am thinking there is some incompatibility issue at the moment with the wireless extension. It is working fine otherwise so it is something not triggering the bell circuitry. What about an extra adsl filter for the wireless extension? Would that make a difference?

[iniltous]

TBH, I’m not familiar with whatever this RTX wireless extension is, is your 706 phone is plugged into this device rather than the physical line socket ? the 706 phone is old technology, designed to ‘ring’ in phase with the 90v AC ringing current sent from the exchange , if this phone isn’t physically wired to the landline , then it’s not likely to ‘ring’, it needs 90v AC to operate the electromagnetic coils that operate the ‘bells’ within the phone ( giving that retro sound )

A modern phone doesn’t necessarily ring in phase with the exchange ringing condition ( ring ring, pause, ring ring ) they simply detect the ringing voltage and do whatever the user has selected in the menu options to signal an incoming call ( some phones play music rather than ‘ringing’ much like a mobile phone )  , your 706 doesn’t detect the signal as such, it uses the the 90v AC , a wireless connection isn’t going to provide that voltage wirelessly

[PaulS69]

The RTX extension has the smaller plug (RJ11) into its base but for the U.K. market comes with an adapter with the socket for the std U.K. phone plug (RJ45?) on the other end to plug the phone into. The socket Jen the base of the RTX wireless extension has 3 visible “pins” whereas the std U.K. socket end has 4 pins. The converted 706 looks to have 6 but it’s transparent and I can see only 4 are connected 

[licquorice]

As @iniltous  has said, unless the phone is physically connected to the incoming line either directly or via a physical extension,it's not going to ring.