700 series bell won't ring on Virgin Hub3

[Christoffrad]

For years I have piggy backed an old 706 phone on my Virgin landline.
Unfortunately the underground line between my house and street cabinet went faulty and they have changed my internet hub to a Hub3 to provide a phone facility. However the ringing no longer works on the 706. I assume either the AC voltage is insufficient or is the wrong frequency or both.

Can anyone tell me what ringing signal the Hub3 generates.
I seem to recall that standard GPO ring voltage was something like 75V of 17Hz.
It was quite nice to know that the phone would still work in the event of a power cut (although of coarse there was no way to dial out) I even was able to receive a call from UK Power Networks during the last power cut.
I suppose the VM street box has no back-up power in the event of a power cut.
It's possible to request a back-up phone from VM but they said it can only make emergency calls.

It would be nice to bring the 706 back to partial use and perhaps build a ringing generator.


Chris

[Graham G3ZVT]

The telephone socket on the Hub 3 is probebly an RJ11 and they supply an adapter cable to with a BT style socket on one end?

Am I correct so far?

If so the problem is with this adapter. Traditionally a master socket had a capacitor coupling the ringing current to pin 3 of the BT plug, but as only vintage phones need it, they don't bother with the capacitor.

There are a number of ways to combat this, one is to rewire the phone internally to use its internal capacitor.

Another is to buy the correct adapter
(example for illustration only)
https://www.ebay.co.uk/itm/262671846092

a third way, and probably the quickest and most convenient if you have one to hand, is to piggy-back an ADSL microfilter with the included adapter.

[Christoffrad]

Graham
Thanks for your reply. However this telephone only requires a two wire connection because it has it's own internal bell capacitor. So I suspect the reason is that the Hub3 does not provide either enough voltage or maybe the ringing fdrequency is not correct. Do you know what it generates. I suppose I could put a scope on it and find out.

[Graham G3ZVT]

Hi Chris,
I would expect an FSX port on an ATA or broadband router to approximate the characteristics of a normal exchange line, and even if the frequency, voltage, avaliable current etc. was non-standard, I would still expect the armature of an electro-magnetic ringer to respond, if perhaps not as strongly as expected.

So, I assume it's not just a matter of adjusting the gongs to match a weaker ring?

The 706 still rings on an normal exchange line?

And a more modern wired phone works when connected to the router's phone port?

This matter of VM switching users to VoIP, and the effect on vintage telephone ringers has become an FAQ on this forum, but the problems are usually resolved without the need for oscilloscopes or additional ringing generators.

[wd40addict]

We swapped to VoIP from our superhub3
in January. The Gecophone, 746 and DECT phones are all working fine including pulse dialling. I have a single ringing capacitor still in the old master socket. Both vintage phones are relying on this capacitor and have 4k bells using series resistor. Has your 706 bell been modified to 4k?

[emeritus]

Some 30 years ago, our hardwired dial phone stopped ringing. It turned out that metal fatigue had meant that the hammer had become detached from the armature of the electromagnet. BT supplied a new pushbutton phone and installed a phone socket for it for free: at that time they normally charged to fit a phone socket. I mentioned it to a guy at work: coincidentally, the hammer on his phone failed a few days later....
.