On Wed, 17 Jun 2015 11:49:01 +0100, Scott M
wrote:

Dave W wrote:
On Tue, 16 Jun 2015 08:06:08 +0100, Scott M

So, thank you Peter for prodding me in the right direction. I knew that
I was a bit on the low side but assumed that a
rectify-and-power-a-sounder ringer would just be a bit on the quiet side
rather than silent

Yes your 40Vp-p was only about 14V rms (if it was a sinewave) which is
normally what is meant by "ac". So 40V ac minimum would be 2.8 times
this p-p, i.e. 112v p-p.

Sinewave? Sinewave!?! We'll have none of those poncy things round 'ere! :-)

It's a fairly ragged square wave and I'd not thought about RMS values.
The web pages covering ringer specs are a bit vague so I'd not thought
about what they were really saying. It's of 50% duty cycle so similar
values to your calcs tho.

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.
--
Dave W

En el artículo , Dave W
escribió:

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.

I thought the ringing frequency was 17.5Hz, but this is from memory, so
could well be wrong. A quick google was inconclusive (some sites
suggest 25Hz, which is conveniently half mains frequency, but I'm not
certain this applies as the ringing current wouldn't have been mains-
derived.)

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

--
(\_/)
(='.'=)
(")_(")

Scott M wrote:
Have promised to lend another local drama group my home brew phone
ringer built from a PIC and a 4 transistor H-bridge driver circuit

Why do you need a PIC? I used a binary counter and a couple of AND gates
to give the waveform:
__ __
__ __ ________

which gated an AC ringing current. This was back in 1988 when I used it
to supply a prop in Japanese lessons, but I've lost the original circuit
during various house moves.

jgh

In article ,
Mike Tomlinson wrote:
En el artículo , Dave W
escribió:

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.

I thought the ringing frequency was 17.5Hz, but this is from memory, so
could well be wrong. A quick google was inconclusive (some sites
suggest 25Hz, which is conveniently half mains frequency, but I'm not
certain this applies as the ringing current wouldn't have been mains-
derived.)

The only geniune Post Office exchange I went round had a long shaft with
two motors (mains and battery) and 17Hz (actually it was c/s then)
generator. So, indirectly mains derived. the battery motor was in case of
mains failure - there was also a big flywheel.

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

--
Please note new email address:

On Wed, 17 Jun 2015 17:54:18 +0100, charles
wrote:

In article ,
Mike Tomlinson wrote:
En el artÃ*culo , Dave W
escribió:

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.

I thought the ringing frequency was 17.5Hz, but this is from memory, so
could well be wrong. A quick google was inconclusive (some sites
suggest 25Hz, which is conveniently half mains frequency, but I'm not
certain this applies as the ringing current wouldn't have been mains-
derived.)

The only geniune Post Office exchange I went round had a long shaft with
two motors (mains and battery) and 17Hz (actually it was c/s then)
generator. So, indirectly mains derived. the battery motor was in case of
mains failure - there was also a big flywheel.

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

Yes I think you're right about 17c/s originally. This website says now
75V rms at 25Hz.: http://www.telephonesuk.co.uk/technical_info.htm
--
Dave W

On Mon, 15 Jun 2015 21:31:10 +0100, michael adams wrote:

The biggest snag will be the variable delay between pressing
"call"
and the on set phone ringing and pressing "hang up" and the onset
phone stopping.

In a strong signal area the delay might be fairly short and
consistent but in marginal coverage it can be several seconds
particularly the "call" stage.

Delays shouldn't be a problem.

The person in the wings only makes the call when he sees the actor
is approaching the phone.

Which may go through in less than a second or take several or even
fail completely.

The phone is only allowed to ring x number of times, after which the
actor picks up the receiver.

If actor has had to wait for a couple of seconds for the phone to
start ringing they ain't going to let it ring... Then you hit the
problem that the phone has been "answered" but the delay from
pressing "hang up" to the remote phone stopping ringing means it's
ringing after being answered.

The fine details could be worked out in rehearsal.

I speak from experience of doing various forms of what the OP is
doing for TV and radio. Mobiles are just not reliable or consistent
enough to be involved in live action, not unless there is a plan to
edit around the inevitable pauses. You can't edit a live stage
play...

--
Cheers
Dave.

In article ,
Dave W wrote:
On Wed, 17 Jun 2015 17:54:18 +0100, charles
wrote:

In article ,
Mike Tomlinson wrote:
En el artículo , Dave W
escribió:

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.

I thought the ringing frequency was 17.5Hz, but this is from memory, so
could well be wrong. A quick google was inconclusive (some sites
suggest 25Hz, which is conveniently half mains frequency, but I'm not
certain this applies as the ringing current wouldn't have been mains-
derived.)

The only geniune Post Office exchange I went round had a long shaft with
two motors (mains and battery) and 17Hz (actually it was c/s then)
generator. So, indirectly mains derived. the battery motor was in case of
mains failure - there was also a big flywheel.

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

Yes I think you're right about 17c/s originally. This website says now
75V rms at 25Hz.: http://www.telephonesuk.co.uk/technical_info.htm

There used to be a feed of Post Office 17Hz (actually 16 2/3Hz) on the bays
at TvC.
--

--
Please note new email address:

In article ,
Tim Streater wrote:
In article o.uk,
Dave Liquorice wrote:

On Mon, 15 Jun 2015 21:31:10 +0100, michael adams wrote:

The fine details could be worked out in rehearsal.

I speak from experience of doing various forms of what the OP is
doing for TV and radio. Mobiles are just not reliable or consistent
enough to be involved in live action, not unless there is a plan to
edit around the inevitable pauses. You can't edit a live stage
play...

One overseas am-dram group I am familiar with was lucky enough to have
a techy who was able to make this device work. Stage Manager pressed
the button, the phone rang with the right tone (ring-ring-pause).
Picking up the phone reset the system and the ringing stopped.

This is the only reliable way to do it.

I have one such device in my "shed". I built it in the early 1970s. It
uses relays to get the "ring pause" bit and a thyratron to generate the
ring tone.

--
Please note new email address:

On Wed, 17 Jun 2015 17:22:39 +0100, Mike Tomlinson
wrote:

En el artículo , Dave W
escribió:

I suspected as much. Come to think of it an 80V p-p squarewave was
probably what the GPO used, by reversing the 40V from their battery at
30Hz, to match the mechanical resonance of old bell clappers.

I thought the ringing frequency was 17.5Hz, but this is from memory, so
could well be wrong. A quick google was inconclusive (some sites
suggest 25Hz, which is conveniently half mains frequency, but I'm not
certain this applies as the ringing current wouldn't have been mains-
derived.)

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.


https://www.youtube.com/watch?v=VzIXvO6RahQ

--

Graham.

%Profound_observation%

Graham. wrote:

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago.

I only went inside a Strowger exchange once (that would probably get my
friend sacked these days) can still remember the noises.

It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

https://www.youtube.com/watch?v=VzIXvO6RahQ

And when the it breaks, you get this

https://youtu.be/ZygIVDql8Bk

Graham. wrote:

On Wed, 17 Jun 2015 17:22:39 +0100, Mike Tomlinson
wrote:

I remember seeing the machine that produced the old 'brrrrr' dial tone
in a Strowger exchange years ago. It was a fascinating piece of kit,
about the size of a washing machine with a half-doughnut shaped clear
plastic cover with what looked like hundreds of contacts and a rotating
disc in the centre. Tried to find a pic online but failed.

https://www.youtube.com/watch?v=VzIXvO6RahQ

That looks familiar. At GEC Trafford Park, they had their own
phone exchange, and in the window was a device very like that.

They had a private link to another Manchester site, for which you
dialled a prefix. The phone booklet showed a similar code for the
link in the reverse direction.

Curiosity whetted, I wondered what would happen if I dialled out,
then back again, and added my own number. It was no surprise that
it was engaged, so I hung up. At this point it all went wrong -
the bell trembled, and when picked up again the line was dead. I
had to request manual intervention. :-(

Chris

--
Chris J Dixon Nottingham UK


Plant amazing Acers.

En el artículo , Graham.
escribió:

https://www.youtube.com/watch?v=VzIXvO6RahQ

Thanks Graham. Not the one I saw though, I think that on in the video
must be a much earlier one. The one I saw was cylindrical and painted
pale yellow/GPO beige.

--
(\_/)
(='.'=)
(")_(")

wrote:
Scott M wrote:
Have promised to lend another local drama group my home brew phone
ringer built from a PIC and a 4 transistor H-bridge driver circuit

Why do you need a PIC? I used a binary counter and a couple of AND gates
to give the waveform:
__ __
__ __ ________

which gated an AC ringing current. This was back in 1988 when I used it
to supply a prop in Japanese lessons, but I've lost the original circuit
during various house moves.

While I like designing stuff in discrete form, the PIC only has 8 pins
compared to 28/32 for a couple of 74/CMOS chips. And a built in
oscillator which does both mark/space and the pukka ring frequency.

--
Scott

Where are we going and why am I in this handbasket?

In article ,
charles wrote:
One overseas am-dram group I am familiar with was lucky enough to have
a techy who was able to make this device work. Stage Manager pressed
the button, the phone rang with the right tone (ring-ring-pause).
Picking up the phone reset the system and the ringing stopped.

This is the only reliable way to do it.

I have one such device in my "shed". I built it in the early 1970s. It
uses relays to get the "ring pause" bit and a thyratron to generate the
ring tone.

Maplin used to produce a kit to make a phone ringer. In the days when they
were interested in electronics.

--
*Ham and Eggs: Just a day's work for a chicken, but a lifetime commitment

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Scott M wrote:
wrote:
Scott M wrote:
Have promised to lend another local drama group my home brew phone
ringer built from a PIC and a 4 transistor H-bridge driver circuit

Why do you need a PIC? I used a binary counter and a couple of AND gates
to give the waveform:
__ __
__ __ ________

which gated an AC ringing current. This was back in 1988 when I used it
to supply a prop in Japanese lessons, but I've lost the original circuit
during various house moves.

While I like designing stuff in discrete form, the PIC only has 8 pins
compared to 28/32 for a couple of 74/CMOS chips. And a built in
oscillator which does both mark/space and the pukka ring frequency.


Problem is being to get the required voltage and current to ring an old
bell phone.

--
*If your feet smell and your nose runs, you're built upside down.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
Scott M wrote:

While I like designing stuff in discrete form, the PIC only has 8 pins
compared to 28/32 for a couple of 74/CMOS chips. And a built in
oscillator which does both mark/space and the pukka ring frequency.

Problem is being to get the required voltage and current to ring an old
bell phone.

Funnily enough, my circuit running off 20v PSU and throwing out 40v P-P
rang various old bell phones just fine, it was the modern warblers that
didn't respond. I was actually very surprised when it worked originally,
expecting that proper coils and clappers would be too much for it. It
was slightly quieter and a little less crisp perhaps but very close and
I was more than happy ith it (and I'm quite finickity about such things!)

--
Scott

Where are we going and why am I in this handbasket?

On Thu, 18 Jun 2015 08:23:33 +0100, Mike Tomlinson
wrote:

En el artículo , Graham.
escribió:

https://www.youtube.com/watch?v=VzIXvO6RahQ

Thanks Graham. Not the one I saw though, I think that on in the video
must be a much earlier one. The one I saw was cylindrical and painted
pale yellow/GPO beige.

Or even Light Straw.

--

Graham.

%Profound_observation%

On 18/06/15 15:13, Dave Plowman (News) wrote:
In article ,
Scott M wrote:
wrote:
Scott M wrote:
Have promised to lend another local drama group my home brew phone
ringer built from a PIC and a 4 transistor H-bridge driver circuit

Why do you need a PIC? I used a binary counter and a couple of AND gates
to give the waveform:
__ __
__ __ ________

which gated an AC ringing current. This was back in 1988 when I used it
to supply a prop in Japanese lessons, but I've lost the original circuit
during various house moves.

While I like designing stuff in discrete form, the PIC only has 8 pins
compared to 28/32 for a couple of 74/CMOS chips. And a built in
oscillator which does both mark/space and the pukka ring frequency.


Problem is being to get the required voltage and current to ring an old
bell phone.

Not really. audio amp and 100v line transformer

Or even a small mains transformer driven back to front.

Not sure what power you need butt class A for occasional use is probaly OK.


--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

In article ,
The Natural Philosopher wrote:
While I like designing stuff in discrete form, the PIC only has 8 pins
compared to 28/32 for a couple of 74/CMOS chips. And a built in
oscillator which does both mark/space and the pukka ring frequency.


Problem is being to get the required voltage and current to ring an old
bell phone.

Not really. audio amp and 100v line transformer

Not exactly a cheap option. ;-)

Or even a small mains transformer driven back to front.

That's how the Maplin unit did it. A complimentary pair of low power
output transistors driving a 6 volt mains tranny in reverse.

Not sure what power you need butt class A for occasional use is probaly OK.

--
*Could it be that "I do " is the longest sentence? *

Dave Plowman London SW
To e-mail, change noise into sound.