How can I connect more than four old telephones?

[jo_marie_denyer]

hi i have read i can omly have 4 old phones working in my house, can anyone explain how i can change this as i am a complete novice,i have 7 old telephones i wont to ring,(at the moment 3 of them wont ring yet they are all wired the same, if anyone can shed some light id be very grateful, ) i have been on the www.britishtelephones.com site but still can find either solutions

thankyou

[Dave Moll]

The actual situation is that you can only have the equivalent of four ringers. All modern equipment has a Ringer Equivalent Number (REN), which is usually equal to one, but some equipment has a higher number. To calculate the maximum load on the system, add these number together. The total should not be allowed to exceed four (though I have got away with a higher total in the past.

Vintage equipment which predates the plug-and-socket system will not generally have a REN marked on it, but can generally be considered to be REN=1 if it contains a bell or other ringer. Some old telephones do not have a ringer - I tend to assume these have REN=0.

If you wish to connect equipment with a total REN in excess of four, the answer is to purchase a telephone booster. This is seen by the line as REN=1, but allows telephones to be connected to its output up to a total of (usually) eight, giving a maximum REN of eleven (its eight plus the remaining three connected directly) This thread may be of some help.

[russell_w_b]

Originally Posted by Dave Moll

The actual situation is that you can only have the equivalent of four ringers. All modern equipment has a Ringer Equivalent Number (REN), which is usually equal to one, but some equipment has a higher number. To calculate the maximum load on the system, add these number together. The total should not be allowed to exceed four (though I have got away with a higher total in the past.

Vintage equipment which predates the plug-and-socket system will not generally have a REN marked on it, but can generally be considered to be REN=1 if it contains a bell or other ringer. Some old telephones do not have a ringer - I tend to assume these have REN=0.

Isn't stuff with a 1000R bell considered to have a REN of 4? Equipment with a REN of 1 has a 4000R ringer in it. In other words, one old telephone with two 500R bell-coils in series will take the full REN of your circuit. You can actually get away with a bigger bell-load if you live near the exchange - or have a DACS (line-sharing equipment) on your circuit.

REN extenders are available, but require a mains-supply (effectively beefing-up the ringing current available). Altenatively, the bells could be disconnected from some telephones until a satisfactory ring is heard from the others.

[ppppenguin]

Originally Posted by russell_w_b

Isn't stuff with a 1000R bell considered to have a REN of 4? .....

Isn't that why we're supposed to put a 3K3 resistor in series with the bell? And hope that it still rings OK.

[igranic]

A telephone can have a REN = 0 if the bell jumper is disconnected on the terminal board inside the the base. Tracing the wire from the ringer coil should indicate the appropriate jumper.

Unless you live in a mansion, it seems unlikely that you would want all of your old phones to ring simultaneously.

HTH

[russell_w_b]

Originally Posted by ppppenguin

Isn't that why we're supposed to put a 3K3 resistor in series with the bell? And hope that it still rings OK.

Correct.

I've never had any bother, volume-wise, with inserting a 3k3 resistor in both 'trimphones' and polarised bell telephones at chez Barnes, 3.5 miles from the exchange. It's often worth snapping up those 8746-series telephones (the 'modern' type 746, made in brown, amongst other colours), as they have 2k bell-coils, giving 4k in total. These coils can be used to replace the 500R coils on more collectable instruments.

[Dave Moll]

Sorry, I forgot to include the bit about the resistor - which I have done entirely successfully with all my 1k ringers - including a trimphone. I was subconsciously assuming that this had already been done if Bob Freshwater's insructions had been followed. As you say, they would otherwise have a REN of four each.

Entirely academic these days, but I believe that the ringers would have been wired in series before the days of plug-in telephones. Therefore the REN would decrease as you added extra 'phones - presumably again up to a theoretical maximum of four.

[AndiiT]

Originally Posted by Dave Moll

.....Entirely academic these days, but I believe that the ringers would have been wired in series before the days of plug-in telephones. Therefore the REN would decrease as you added extra 'phones - presumably again up to a theoretical maximum of four.

The ringers were indeed wired in series in the days of hard wired phones. The GPO used to specify a total of six telephones on a direct exchange line or three in the case of a shared service (party) line, the length of line/distance from the exchange and the type of ringing equipment used at the exchange was also a contributing factor.
As the GPO charged additional rental for every extra extension I doubt if there were many domestic installations with more than two phones in total.

These days the maximum REN of 4 is only a guideline, some installations will work quite happily with six phones while others struggle with four.
There can also be problems where a capacitive (i.e. tone caller) and inductive (i.e. Bell) ringing devices used on the same line will give poor or no ringing.

An alternative way of getting around the problem of ringing a number of phones is to try and obtain an electronic PBX, possibly from one of the internet auction sites or one of the many suppliers on the net, as most of these will happily work with both 1k and 4k ringers; If you do go down this route ensure that the PBX will operate with standard POTS telephones and not just "dedicated" terminal equipment.

A lot of small PBXs will happily ring up to ten phones simultaneously (depending on the configuration)

In my experience Trimphones are very hungry for ringing current even when the 3k3 resistor is fitted in series with the tone ringer; I think a Trimphones average REN is around 3



Andrew