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Old 25th Feb 2011, 12:05 am   #1
BakeliteBear
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Default REN Booster

Does anyone have any experience of sourcing and fitting a REN booster to a domestic telephone line?

I have few too many vintage telephones for the normal circuit to drive them all - and yes I have fitted the 3.3k resistor! Thanks.
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Old 25th Feb 2011, 11:58 am   #2
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Default Re: REN Booster

BT used to sell these -- one cos tme about £40 a few years ago. Quick & easy to install as I had to rewire most rooms in the house to accept the phone connection that Sky demand.

HTH

Phil
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Old 25th Feb 2011, 6:37 pm   #3
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Default Re: REN Booster

I also purchased one some years ago. All the wiring for extension sockets around the house is connected to the output of the booster - as I too have lots of old 'phones around the house.

My arrangement is: master socket -> ADSL filter -> booster -> extensions.
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Old 25th Feb 2011, 9:24 pm   #4
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Default Re: REN Booster

Hi,
I have seen REN boosters in use and they seem to work fine, as long as they are wired correctly.

An alternative would be to purchase a small electronic PBX such as a Minmaster 3, Revelation or something similar; this allows a lot more options as the ports of a lot of these systems have a REN of 4 to begin with so if you have a system with 8 extension ports you could, in theory, wire up to 32 telephones to ring.

You also get the advantage of call hold and transfer facilities if you connect one of these to your main exchange line, some of these units can also perform pulse to tone conversion before sending the digit string out to the line.

Another "cheaty", but possibly not too reliable, method of boosting REN is to use master sockets, which have their own built in ringing capacitor, at each telephone - BT had at least one small keysystem which required this method due to the limitations of the built in ringing generator.

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Old 25th Feb 2011, 9:40 pm   #5
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Default Re: REN Booster

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Originally Posted by AndiiT View Post
Another "cheaty", but possibly not too reliable, method of boosting REN is to use master sockets, which have their own built in ringing capacitor, at each telephone
Do I infer from this that a telephone using an internal ringing capacitor (i.e. wired for two-wire operation) would have a similar effect? I had always assumed conversely that such a unit would contribute towards the total line REN even if connected downstream from the booster.
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Old 25th Feb 2011, 9:55 pm   #6
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Default Re: REN Booster

Quote:
Originally Posted by Dave Moll View Post
Quote:
Originally Posted by AndiiT View Post
Another "cheaty", but possibly not too reliable, method of boosting REN is to use master sockets, which have their own built in ringing capacitor, at each telephone
Do I infer from this that a telephone using an internal ringing capacitor (i.e. wired for two-wire operation) would have a similar effect? I had always assumed conversely that such a unit would contribute towards the total line REN even if connected downstream from the booster.
You will get a simular effect, but the smart thing with your master socket system is to limit the ring current, and tinkeling.

Try to hook on a 1.8 (2) μF capacitor (or somthing near 1-2 μF you have in the house) in paralell with the exisisting one in your master socket. This will definitly increase the capacity of ringing, and probably within what the supply may deliver.

dsk
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Old 25th Feb 2011, 9:57 pm   #7
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Default Re: REN Booster

Hi,
There is no reason that a telephone wired for two-wire operation would have the same effect as using Master sockets, I did mention in my post that this may not be too reliable however.

Taken from here

"Due to limitations of the Renown ringing generator, each extension port effectively has an output REN of 2. Contrary to normal practice, any additional sockets on Renown extensions will need to be Master Jacks to optimise ringer output."

Whilst the above relates to a small electronic PBX, it should still apply to a PSTN line.

I guess I could do a few "home experiments" and see how many telephones I could get to ring using just master sockets

Andrew
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Old 25th Feb 2011, 10:29 pm   #8
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Default Re: REN Booster

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Originally Posted by AndiiT View Post

I guess I could do a few "home experiments" and see how many telephones I could get to ring using just master sockets
Done that (well, similar...), results attached. The cap(s), wherever it is (they are), part-resonates the bell(s) and govern the current drawn, so forming part of the REN.
Attached Files
File Type: doc Telephone Loading Impedances.doc (72.5 KB, 424 views)
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Old 25th Feb 2011, 11:58 pm   #9
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Default Re: REN Booster

Can anyone recommend a current source for a REN booster?
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Old 26th Feb 2011, 9:36 am   #10
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Default Re: REN Booster

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Originally Posted by BakeliteBear View Post
Can anyone recommend a current source for a REN booster?
The BT REN booster I have (not used currently) isn't actually a ringing generator, but reinforces the ringing signal outgoing from the booster by detecting it and triggering a +VE or -VE pulse to coincide with the incoming +VE and -VE ringing waveform.

The reinforced ringing current is derived from a mains-powered PSU inside the booster unit.

In other words, it takes the application of a ringing voltage input from the line to create a reinforced (lower-impedance) ringing supply to one's telephones. Maybe other REN boosters work differently?
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Old 26th Feb 2011, 12:26 pm   #11
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Default Re: REN Booster

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Originally Posted by BakeliteBear View Post
Can anyone recommend a current source for a REN booster?
I took this question to mean that BB is asking where they can currently be sourced, rather than where a current could be sourced. Unfortunately, I am unable to give a satisfactory answer to this question, as I haven't seen one advertised (even second-hand) for quite some time.
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Old 26th Feb 2011, 2:14 pm   #12
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Default Re: REN Booster

Four candles...

Do a 'Google' (UK) and they turn up places.
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Old 26th Feb 2011, 2:44 pm   #13
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Default Re: REN Booster

http://www.limitedgoods.com/itemView...ogleUK_InStock

Not cheap I'm afraid.
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Old 26th Feb 2011, 3:20 pm   #14
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Default Re: REN Booster

Quote:
Originally Posted by russell_w_b View Post
Quote:
Originally Posted by AndiiT View Post

I guess I could do a few "home experiments" and see how many telephones I could get to ring using just master sockets
Done that (well, similar...), results attached. The cap(s), wherever it is (they are), part-resonates the bell(s) and govern the current drawn, so forming part of the REN.
This is quite complicated, but I have an idea about, instead of that series resistor, just producing heat, a capacitor of e.g 1 ĶF will do the job, but not use any effect. If we dont use the effect for heating, it may be used for ringing.
If someone with skills could please calculate the effects there of, I would be happy.

dsk
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Old 26th Feb 2011, 4:15 pm   #15
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Default Re: REN Booster

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Originally Posted by russell_w_b View Post
Four candles...

Do a 'Google' (UK) and they turn up places.
I have done, but all the reasonably priced boosters seem to be no longer in stock; I guess there is no call for them with modern telephones drawing so little current.

The only one available is around £150 and at that price my old telephones will stay unplugged!!
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Old 26th Feb 2011, 4:17 pm   #16
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Default Re: REN Booster

Quote:
Originally Posted by Dave Moll View Post
Quote:
Originally Posted by BakeliteBear View Post
Can anyone recommend a current source for a REN booster?
I took this question to mean that BB is asking where they can currently be sourced, rather than where a current could be sourced. Unfortunately, I am unable to give a satisfactory answer to this question, as I haven't seen one advertised (even second-hand) for quite some time.
Yes thatís what I meant!
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Old 26th Feb 2011, 7:58 pm   #17
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Quote:
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Yes thatís what I meant!
1: Sandman has somthing: http://www.sandman.com/longloop.html
Expensive too.

2: If you have ringer suplpy, e.g. a frequency dividing transformer, and a relay, you may make one.

3: I have a wireless phonejack. http://www.wireless-phonejack.com/
It works OK and gives about 3 REN extra. (It draws 0 REN)

4: The best would be a PABX. Panasonic KXT 308 or 616 is quite good.

dsk
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Old 27th Feb 2011, 1:54 am   #18
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Default Re: REN Booster

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'This is quite complicated, but I have an idea about, instead of that series resistor, just producing heat, a capacitor of e.g 1 ĶF will do the job, but not use any effect.'
There will always be an effect where capacity and inductance are connected.

Are you suggesting a different value for your master box capacitor (common to all instruments) or are you suggesting using a capacitor to replace the resistor in each telephone? If the former, then the total impedance provided by one telephone and a 1uF cap in the master box (as opposed to a 2uF cap in my earlier post) would be (typically with 59A bell-motor: R=1549 Ohms, Xl = j2032) Z = 4603, which could draw a theoretical maximum of 16.3mA. It would never achieve this, of course, because of line and source resistance, maybe 1000 Ohms or more.

Note that the figures in my earlier post are theory backed up with a practical experiment on a low-impedance ring generator, and I have not factored in line resistance, assuming 75V RMS at the telephone input!

Now, if four instruments were connected to the modified master box (1uF instead of 2uF), each without the 3k3 resistor, the total impedance presented would be Z = 5871, allowing a theoretical current of 12.8mA. But that current would be divided by four, so each telephone would draw a paltry 3.2mA - far too low to ring a magneto bell.

If you are suggesting keeping the master box at 2uF and replacing the 3k3 resistor in each telephone with a 1uF capacitor (for example) then the total capacitance will always be less than the smallest capacitor used, in this case it would equate to 0.67uF for one telephone, so the total impedance presented would be Z = 7629, allowing a theoretical max. current of 9.8mA. Four telephones would present a total impedance of Z = 4406, with a total theoretical line current of 17mA, or 4.2mA each instrument - again, hardly enough to ring the bell and less than it would be - just! - if 3k3 resistor were used in each telephone instead.

The trouble with capacitive dropping is that there is an element of resonance whereby the impedance changes with combinations of capacitors and bell-motors (a typical 59A bellset has an impedance of 1549 + j2032, or Z = 2555 phase-angle 52.7 degrees. When resonated with a series capacitor of 2uF, the total impedance presented to the line is 1549 -j1505 (Z = 2160 phase-angle -44 degrees. This part-resonance increases the current flow to a theoretical maximum of 35mA, compared to 29mA without the capacitor.

Resistive dropping offers the consistency that reactive dropping doesn't. I once experimented with 'tuning' a bell-motor with a parallel capacitor to increase dynamic resistance and so reduce current, until it was pointed out to me that I had overlooked the capacitive shunt effect on speech that would occur as a result of wiring a cap directly across the bell in series with the master-box capacitor!

For less than two telephones, I would forget the resistor anyway - I've always found they work without! If you live near an exchange, this may well hold with four.
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Old 27th Feb 2011, 8:45 am   #19
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Default Re: REN Booster

Both,
A max at about 4 μF in the master socket.
The 3k3 resistors replaced by a 0,5-1 μF depending on ringer.

dsk
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Old 27th Feb 2011, 11:36 am   #20
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Default Re: REN Booster

Quote:
Originally Posted by dagskarlsen View Post
Quote:
Originally Posted by BakeliteBear View Post
Yes thatís what I meant!
4: The best would be a PABX. Panasonic KXT 308 or 616 is quite good.

dsk
Can you please talk me through how that might work. I have no experience of exchanges, but plenty of working on telephones, so back to basics please.

Incidentally it seems I can buy an exchange rather less expensively than a REN booster!!
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