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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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4th Feb 2020, 4:58 pm | #1 |
Tetrode
Join Date: Jan 2020
Location: Canterbury, Kent, UK.
Posts: 71
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The ding effect
Hello,
I've two questions, one of which ( for the majority of users on this forum ) will I'm sure be a piece of cake, the other maybe not. I'll post the second question separately, but for now: we have four telephones, all of which I'm fairly sure are the old-style 782 type ( DMTF dialling including # and * keys ). When you pick up the receiver on one of these, any given one or combination of the others will 'ding' randomly; sometimes they do it, sometimes not. On a couple of the phones, the actual bell in the telephone you're picking up will do it when you lift the receiver. I'm pretty sure this is a relatively simple fix; in fact, I've got a feeling I've probably done it myself in the past ... something along the lines of inserting a resistor or capacitor across two of the terminals where the line comes into the phone ...? Not quite sure, but that's where you come in! If anyone can enlighten / remind me, it will be appreciated! By the by, as per an earlier post, incoming volume is very much an issue on these phones due to our distance from the exchange, so could you let me know whether any suggested fix might have any possible detrimental effect on that? ( I'm guessing not, inasmuch as presumably the 'ringing' current comes in on different terminals than the 'speech' current ... but as you gather, I'm far from expert in these things!! ) As always, any input gratefully received. |
4th Feb 2020, 6:44 pm | #2 |
Tetrode
Join Date: Jan 2020
Location: Canterbury, Kent, UK.
Posts: 71
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One phone at a time!
Following on from my earlier post … so: we’ve got four telephones which I’m reasonably sure are all BT 782’s ( DTMF dialling with # and * keys, various ages ). Depending on the answer to my previous query about the ‘ding effect’ ( or to be more accurate, depending on whether the answer to that has any bearing on the answer to this ) ...
I’ll admit up-front that this is another one like the previous telephone-amplifier question, to which I suspect the answer is basically just ‘no’. However, on the off-chance: Is there any way to configure the phones in question in such a way that when one phone is in use, the others are effectively disabled until the receiver is replaced on the phone being used? The phones are in quite separate areas of the house, and it’s frustrating to be constantly coming in in the middle of other people’s conversations! |
4th Feb 2020, 8:31 pm | #3 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: The ding effect
The "ding" is caused by the change of voltage across the line when a telephone goes "off hook". Given that the bell is energised by the changing voltage of the AC ringing current, this smaller change in voltage may be enough to cause the armature to move once.
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4th Feb 2020, 11:17 pm | #4 | |
Heptode
Join Date: Jul 2007
Location: Flintshire, UK.
Posts: 707
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Re: One phone at a time!
Quote:
There used to be a small device known as a 'privacy' adapter which you plug into a socket - then you plugged two phones into the adapter. If one phone was in use, the other phone couldn't be used/ overhear. Can't remember if it worked with more than one pair of phones. ] To get around the problem, why not fit a small one exchange line, up to 8 extensions PABX (you need to wire four up) and it will solve the problem plus the ability to transfer calls or call between phones. PABXs come up on eBay quite cheaply - I picked up a Panasonic 3 line 8 extension system for 99p plus 6.99 carriage. Keep our eyes open. Ian J |
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5th Feb 2020, 2:28 am | #5 | ||
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,715
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Re: One phone at a time!
Quote:
Quote:
I have a compromise arrangement now, the wired POTS phones in the lounge, hall, kitchen, and bedroom are in parallel on ext 301 There is a DECT handset on 302 and my "private" POTS phone on 303. Two Android phones run CSipSimple on 303 & 304 and work inside or outside the LAN.
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5th Feb 2020, 2:37 am | #6 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,715
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Re: The ding effect
The technical term is not "ding" I mean that's just silly.
It's "tinkle"
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5th Feb 2020, 9:55 am | #7 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: The ding effect
The first question is how are they wired 1: as a plan 1A ( old style hard wired )
2: new plan with sockets the 1st needs 4 wires this includes a anti tinkle wire that shorts out the bell . The second requires 3 wires but the REN of the phone needs to be increased by fitting a 3K3 resistor in series with the bell and a master socket Dave
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5th Feb 2020, 10:13 am | #8 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: The ding effect
Let's unpick that a bit.
Surely, the "old plan" had bells in series and thus didn't need an "anti-tinkle" wire. One end of the internal ringer was connected to the green wire so that either an external ringer or a shorting link (if no further ringers) could be connected between it and the white wire. A fourth wire was only needed when an earth connection was required (e.g. for shared service or for recall on a PBX). With new plan the bells are connected in parallel via the blue ("anti-tinkle") wire to an external capacitor in the master socket. The purpose of a series 3.3K resistor bodge is effectively to reduce the REN of an individual telephone* so that up to four can be connected in parallel without exceeding the maximum permitted REN of 4. *I refer to this as a bodge, as the official modification was to replace the 1K ringer with a 4K one.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
5th Feb 2020, 11:26 am | #9 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: The ding effect
The N diagram N4502 shows 4 wires A & B for the line G for bell and Bn for bell tinkle
Dave
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5th Feb 2020, 1:25 pm | #10 |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: The ding effect
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5th Feb 2020, 1:28 pm | #11 |
Tetrode
Join Date: Jan 2020
Location: Canterbury, Kent, UK.
Posts: 71
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Re: The ding effect
I'll look at the 'ding effect' posts for now, as I think the other problem is going to be a whole other ball game.
For the record, I'm sticking with 'ding' rather than 'tinkle' because 'ding' implies a single strike of the bell, whereas 'tinkle' implies more than one. That's my story and I'm sticking to it. Also for the record, I'm old enough to remember party lines first-hand; not that we ever had one, as far as I can recall, but I was around when they were. To give you some idea, our first phone had an exchange name followed by a three-digit number. Those were the days ... I digress. Surprisingly, for someone who acquired the bulk of their electronic knowledge from a Philips Electronic Engineer at the age of around nine or ten ( give or take ), I do actually get some of this, even down to the circuit diagrams obligingly provided - the operative word being 'some'. I do, for example, understand Dave's explanation of why the 'ding' ( still going with 'ding' ) happens in the first place. To answer nutteronthebus ( I feel weirdly disrespectful using that name for someone clearly more knowledgable on the subject than I am ...! ), this is where it all starts to get a bit blurry for me. I don't know the plan numbers you mention, but the phones are all plug-and-socket., so plan 2, I guess. From the words 'the first needs 4 wires ...' to pretty much the bottom of the page, the rest is a mixture of bits I do understand and bits I don't. I can more or less read a circuit diagram, which is to say I know a capacitor from a diode - I even know more or less what a capacitor and a diode do - but the exact function of each component within the complete circuit is above my pay grade, which implies that I ever had a pay grade relating to this type of work, which I didn't. To give you an example, I know that a 3.3k resistor will reduce the REN ... I'm just not entirely sure why. If - and I do say 'if' - I've gathered correctly, the solution to this problem is going to depend on how the incoming line is 'strapped' ( correct term? - apologies if not ) in the first place; which in turn means I'd have to open up each of the phones, take a photo of the connections at the back, and post the photos on here ( it being the case that all four phones were bought separately and may very well not be strapped identically ). Or am I over-thinking this and there's a far simpler solution? |
5th Feb 2020, 1:44 pm | #12 | |
Heptode
Join Date: Jan 2008
Location: Hakadal, Norway
Posts: 643
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Re: The ding effect
Quote:
https://www.epanorama.net/circuits/tele_privacy.html You may use a quadrac instead, then you just follow the same chemeatics, but the diac is not needed and may just be a wire. You need one quadrac in each telephone, but it is so small that you will always get the room you need for it. For those who use modems or ADSL, this may even reduce the phones reduction of the data speed. dsk Last edited by dagskarlsen; 5th Feb 2020 at 1:46 pm. Reason: adding info |
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5th Feb 2020, 9:00 pm | #13 | |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: The ding effect
Quote:
Doing so would certainly be helpful. 700 series telephones are not difficult to open up.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
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5th Feb 2020, 10:20 pm | #14 | ||
Heptode
Join Date: Jan 2008
Location: Hakadal, Norway
Posts: 643
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Re: The ding effect
Quote:
The only thing I am missing in that hence is the need of approximately equal equal power draw on equal phones. By my opinion the use of a series capacitor will result in less loss of power, but it will also be difficult to calculate. North American phones uses about 1/2 microFarad so adding an extra 1 uF in series with each ringer could be a start. dsk |
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6th Feb 2020, 9:30 am | #15 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: The ding effect
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Any tool can be used as a hammer but a screwdriver makes the best chisel |
6th Feb 2020, 9:55 am | #16 |
Heptode
Join Date: Feb 2010
Location: Duffort, Gers, France
Posts: 714
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Re: The ding effect
To give someone a tinkle was quite a common expression at one time. There was even a song "Will Willy tinkle Tilly on the telephone tonight". I suppose language evolves.
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6th Feb 2020, 6:14 pm | #17 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: The ding effect
"Ding" on pickup is just a subset of "Tinkle" which is a reasonable description of the sound you would get from parallel wired 'phones' bells when dialling out using a real loop disconnect dial. Tinkle as a word I suspect originated in the bell arena and has subsequently been applied to other, similar sounding, activities. A suitable amount of thought was exercised in the early days of dialled telephones in order to get rid of this and other undesirable problems. Nowadays the sound of the DTMF tones as you push buttons is a lot easier on the ear than the explosive pulses you would have got from a phone with no or malfunctioning dial "off normal" contacts shorting out the receiver.
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7th Feb 2020, 9:39 am | #18 |
Heptode
Join Date: May 2014
Location: Salisbury, Wiltshire, UK.
Posts: 998
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Re: The ding effect
We always used "tinkle" at home...I'll give you a tinkle later..
Tinkle is much more poetic than ding.
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7th Feb 2020, 10:37 am | #19 | |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,687
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Re: The ding effect
Quote:
I've always referred to the sound as a 'ting' (single) or a 'tinkle' (multiple). A 'ding' is what you get in a car when you bash it. A 'ting' used to happen of a night about midnight, during automatic line testing, where I believe the line polarity was momentarily reversed. I used to kid my mam on that the line was being tapped!
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7th Feb 2020, 8:48 pm | #20 | |
Heptode
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 805
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Re: One phone at a time!
Quote:
This might require a Tele 740 or at least an extra hookswitch, and I don't think it was a standard Plan. The first phone on the line would have secrecy against all phones lower down the chain, but would interrupt an existing call. The "privacy adapter" mentioned by dagskarlsen, or a smilar circuit, is probably easier. |
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