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Old 1st Oct 2007, 8:06 pm   #1
phillrogers
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Default Problem with bellbox

I've got a little problem with the bellbox fitted in my house. I have a couple of pulse dialing 'phones (706 and Viscount) and a more modern DTMF DECT 'phone. When either of the pulse dialing 'phones are connected and a number dialled, (intermittant) pulsing can be heard on the bellbox's bells. In all other respects the apparatus ('phones and ringer) work without fault.

I'm guessing (rather niave no doubt!) that this was a common fault of yester-year(?). I presume that some kind of 'smoothing' is required to essentially filter out the pulses(?) - perhaps that is what the jumper plates are used for (?). Anyhow, I'm not well versed in this well-made vintage equipment and would be very grateful for some suggestions as to how to 'cure' this problem (symptom).

There are only two connections to the bellbox - see attached picture. I have not modified the connections in any way.
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Old 1st Oct 2007, 9:39 pm   #2
russell_w_b
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Default Re: Problem with bellbox

Quote:
Originally Posted by phillrogers View Post
I've got a little problem with the bellbox fitted in my house. I have a couple of pulse dialing 'phones (706 and Viscount) and a more modern DTMF DECT 'phone. When either of the pulse dialing 'phones are connected and a number dialled, (intermittant) pulsing can be heard on the bellbox's bells. In all other respects the apparatus ('phones and ringer) work without fault.

I'm guessing (rather niave no doubt!) that this was a common fault of yester-year(?). I presume that some kind of 'smoothing' is required to essentially filter out the pulses(?) - perhaps that is what the jumper plates are used for (?). Anyhow, I'm not well versed in this well-made vintage equipment and would be very grateful for some suggestions as to how to 'cure' this problem (symptom).

There are only two connections to the bellbox - see attached picture. I have not modified the connections in any way.
Hmmm... 'Tinkle-bell', eh?
  • Has your bell-box always done this?
  • Is this intermittent tinkling concomitant with dialling pulses, or just random?
  • Does your 706 'tinkle' when you pulse out on your Viscount?
  • You say you haven't modded the wiring. Have you fitted ADSL filtering at your sockets connected to your exisiting telephones?
  • Have you got line-jack unit sockets or hard-wired connections?

If you have ADSL filters, the third wire (number 3 on the LJU rear connections) is dissed from the plugged-in telephone's bell-wire; each ADSL filter acts like a little master-socket of its own, with its own little bell capacitor included. If this is the problem, you can get around it by fitting a master LJU filtered faceplate, so that any sockets downstream of the master are filtered by the one filter, and the third wire is intact relative to all extensions and bells.

Of course, it might be something completely different!
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Regds,

Russell W. B.
G4YLI.

Last edited by russell_w_b; 1st Oct 2007 at 9:41 pm. Reason: Undue haste resulted in misplaced apostrophe; tch!
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Old 1st Oct 2007, 10:49 pm   #3
AndiiT
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Default Re: Problem with bellbox

Hi,
It sounds to me like you have the bell and other pulse dialing equipment connected in "two - wire" mode. This will give rise to Bell tinkle on any of the equipment that is fitted with a Bell (it may also be possible to hear some tone callers "bleep" intermittently whilst dialing out depending on your installation.

No extra smoothing is required, it may be that the Bell set isn't the cause of the problem but more likely an incorrectly wired 706 or other pulse dialing phone. The straps on the Bell set are purely for different combinations of wiring depending on how the original extension "plan" (which is what the GPO called them) was set up.

In the days when pulse dialing was the norm and "proper" AC Bells were used the bells were "Low impedance" (around 1k ohm) and wired in series in the bell circuit - with the advent of the "new" plug and socket system introduced in 1982 the Calling devices, either integral to the telephone or external, became "High Impedance" devices (around 4k ohm) and were now wired in parallel.

The first thing I would try is to extract the ringing supply from terminals, if you have not already done so, from terminal 3 (hot) and 5 (common) on the master socket or one of your extension sockets, providing that these are wired correctly and that no ADSL filters are used, as has been suggested elsewhere in this thread.

Commonly used colours are Orange/White from terminal 3 and White/Blue from Terminal 5 (some installers will use White /Orange to maintain convention but as long as you connect to terminals 3 and 5 colour convention isn't really a problem - I have included this for the sake of completeness)

Remove strap B5 - B4 from the Bellset and replace strap B2 - B3 with a 3k3 1/4 watt resistor, connecting your "ringing supply" to B1 - B3 (which is what you have already done anyway by the look of the enclosed picture.

The following may also help http://www.samhallas.co.uk/repositor.../0000/N550.pdf

Regards
Andrew

Last edited by AndiiT; 1st Oct 2007 at 10:54 pm.
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Old 2nd Oct 2007, 1:31 pm   #4
phillrogers
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Default Re: Problem with bellbox

Hello Russell and Andrew,

VMT for your comments and suggestions. It would appear that you were both quite correct: the ADSL setup was causing the problem, and Andrew's suggestions helped to solve it.

FYI there are two 'phone sockets in my house: a master and a secondary. The bellbox is fed off the master. I have a ADSL router connected to the secondary and the Viscount connected to the master. Both master and secondary have ADSL filters in place. When the master's ADSL filter is removed everything works, but, when the internet is on there is a slight 'hum' from the Viscount's earpiece.

I'm not sure whether not having an ADSL filter offers any dissadvantage since I can still use the internet without any apparent problems and can still make and receive 'phone calls using the Viscount.

So I twisted two 1/8W 10k Rs in parallel and substituted them for the B2-B3 jumper. Hey presto! There's no more bell-tinkle!

Thanks very much for your wise comments.

Phill
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