Sunday

The Pulsynetic C69 programmable impulse timer. (Bell Ringer)

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One very useful accessory for Pulsynetic impulse clock systems was the adjustable programmer. Perhaps more commonly known as a "bell ringer".  Which was its usual task in schools.

This device could be used to ring electric bells and and sound factory sirens. It was commonly used in schools to mark the beginning and end of classes thanks to its reliability and accuracy. By removing the human element, classes, or other regular events, could be timed, almost to the second, almost indefinitely. Moreover the bells would ring simultaneously throughout the entire school without human intervention.



The Gents' Pulsynetic programmable contact maker.

The programmer relies on a beefed-up version of the Gent's slave dial mechanism. Through a simple system of gears the programmer's large ring is advanced at half minute intervals by the slave mechanism. On the impulse dial mechanism itself is the minute dial. Large slaves like this were sometimes used for larger public clock dials. Though usually the hands would be behind glass to avoid "weather resistance" to the limited torque available.


The very large ring at the rear has holes at 5 minute intervals where tapered pins can be inserted to actuate the electrical contacts. (on the extreme left in the top image) The disk on the left is the day of the week dial which allows the contacts to close. Or via a simple cam on its edge blocks them from closing. By this means the bells can be silenced during the weekend when the school is normally closed. A push button (at bottom left) allows the bells to be rung continuously as an alarm. Perhaps in the case of a fire drill or other emergency. The programmer was usually installed near the master clock in the headmaster's office or the school secretary. Security from tampering is thus assured.

The rocking mercury switch provided a fixed and limited period of bell ringing of 7-8 seconds. Without it the bells would ring continuously, once closed, until the pin finally cleared the contacts.


The Pulsynetic bell ringer. Or programmable contact maker.
Left click for much larger image. [300kB]

Full description:  The contact maker can be thought of as a clock, or time switch, with three dials which rotate against fixed pointers. These indicate the day of the week as well as showing the (24 hour) time and the minutes of the hour:

The electromagnet is activated by the master clock's brief impulses at 30 second intervals. This part of the mechanism is a modified, heavy duty, double locking, slave dial movement. The minute wheel and star wheel are rotated by the ratchet (or impulse) wheel as one unitAll three turn once per hour driven by the electromagnet. The purpose of the 12 point star wheel is to continuously lift and reset the mercury switch and then release it again at 5 minute intervals.

The mercury switch fixes the duration of bell ringing to about 8 seconds. This is achieved by the mercury running slowly back, through narrow channels, away from its internal electrical contacts.

The day of the week wheel is really a simple cam driven by a pinion on the 24 hour wheel. The day of the week wheel has a normally-closed, bronze, contact finger rubbing along its lower edge. At the weekends an optional cutaway on the edge of this wheel allows these sprung contacts to open. Thus breaking the bell circuit. Which stops the bells ringing all weekend until the raised edge finally returns on Monday. Closing the contacts again.

Weekend silencing is a mechanical option. Gent's used to say that changing the programmer had to be attended to by their own engineers. Ringing is dependent on the weekend contacts being closed. This can cause some confusion in new owners/clock carers who cannot understand why the bells don't ring when a pin is set. A glance at the bottom of the day of the week dial should confirm whether weekend silencing is active.

Careful examination of the day of the week wheel in the image above shows that I have turned the removable back plate. The day of the week contacts remain continuously closed. Allowing ringing at weekends as well. The thin grey line of the back plate can be seen in the normally cutaway weekend sector. Removing the retaining pin and bush from the day of the week wheel will allow access to the backplate. Be very careful if you are tempted to try this. There is a large and heavy, bronze, toothed wheel (gearwheel) behind the day of the week wheel. As you slide the wheel free be ready for the unexpected weight. You will also need to reset the day of the week accurately when you replace it! (see setting instructions below)

The 24 hour pin wheel has holes around the periphery at 5 minute intervals. It is driven by a pinion from the minute wheel of the slave movement. When a stout, tapered, timing pin is placed in any of these holes it will eventually arrive at the bell contacts at the extreme left  of the mechanism. The pin closes the contacts, completing the bell circuit at the time shown on the pin wheel dial.Being a 24 hour dial the pins must be placed where they will cause the contacts to close only at a desired time. So pins are usually only required during the working hours of the school. So no pins are fitted during the evening or hours of the night. This simple arrangement allow night silencing without the extra complexity of driven wheels, cams and contacts.

Any single contact in the programmer's circuit cannot ring the bells. All must be closed at the same time. The bell contacts are closed by the timing pin for several minutes. The mercury switch is then released by the star wheel. Only if the weekend contacts are closed will an applied low voltage DC current pass through the entire bell circuit. Note that the bell circuit has no connection to the clock impulse circuit. Separate, labelled connection terminals are provided for both circuits (time and bells) at the front, inside the secure case. 

If a heavy current, or a higher voltage is required to be switched, then a suitable relay may be switched by the low voltage bell circuit. One should not try to switch mains electricity or higher voltages DC with the programmer's bell circuit. Higher voltages will cause arcing and should be strictly avoided. These higher voltages would make exposed metal, screws and wires live! Which could easily prove lethal if touched accidentally! A fire is also entirely possible due to overheating of components. 

Programmer time and day setting: Thanks to the clear markings on the various wheels the time and day of the week can be read off the programmer. Naturally these wheels must all be set accurately when the bell ringer is put into use. The day of the week wheel may be set quickly by removing the tapered pin and bush which retain it on its arbor. Do not lose these parts. The day of the week wheel may then be drawn gently forwards and out of engagement with its drive pinion. Then turned to the desired day before being very gently pushed backwards again to engage the large, toothed wheel with its driving pinion. The exact placement (rotation) will depend on the time already showing on the other two wheels.

It is easiest to set the day of the week dial at a particular time since it lacks any other sub-divisions than midnight between any two days. Midnight may be easiest to set accurately but is hardly a user-friendly time to be setting the mechanism. Using other times will require some guesswork. The time of day on the day of the week wheel is read from the point where the weekend contact finger rests underneath the wheel. So setting the day of the week wheel is best carried out at 6 or 12 o'clock. Being a quarter or halfway through the day shown against the bottom pointer. Midnight would of course be on the line between two days. Once set it will continue to rotate with the mechanism and show the correct days of the week. So setting only needs to be done once and can be checked for absolute accuracy if you should happen to be around at midnight. Check that the other dials agree that it really is midnight. Remember to replace the retaining drilled bush and tapered pin before you lose them. 

The minute wheel may be advanced by repeatedly pressing the armature against the electromagnet core and releasing it briefly. The slave movement which drives the entire mechanism has double locking. This makes it very difficult to advance quickly. (Unlike a normal slave which needs only the electromagnet armature to be pressed in to release the ratchet wheel)

There are certain midpoint positions of the locking and impulse levers which will allow the ratchet wheel to turn freely. But it requires some care and dexterity to avoid graunching the ratchet wheel with the levers if they should suddenly re-engage! Probably no damage will be done but it isn't a kind way to treat such a fine, old mechanism.

Freeing the minute wheel will also allow the 24 hour pin wheel to turn as they are geared together. The time on the 24 hour pin wheel is read at the bell contacts whether a pin is present or not. A pin may be inserted temporarily to ensure accuracy of reading the time showing on the 24 hour dial. There should be no disagreement between the time shown on the minute wheel and pin wheel unless the mechanism has been previously dismantled.

A black pointer is provided to show the time on the minute wheel of the slave movement. (Accurate only at the half minute time impulse)

Although the contact device is commonly known as a bell ringer it may be employed to switch low voltage currents for any purpose. You could even use it as an alarm clock with a suitable low voltage doorbell or buzzer. Or to switch lights on and off via a locking relay. 

Mercury


Great care should be taken with the glass, mercury switch. It contains liquid mercury within a thin glass envelope. It is held by strong spring clips but can slip free if touched.  Mercury vapour is highly toxic. Liquid mercury must never be allowed to remain if spilled indoors. The mercury switch is very shiny and the flowing metal very unusual in appearance. This may make the switch attractive to curious children. It is strongly suggested that the programmer case door be kept locked at all times and the key kept somewhere secure and completely inaccessible.

Mercury Spill Response -- Cleaning Up Small Spills


Click on any image for a larger version. Back click to return to the text.
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19 comments:

Anonymous said...

Hi,
I recently stumbled on a very similar programmer in an old school building. Mine has a more recent electric motor, though. I'd be interested to know about them.

Chrisbee said...

Hi

Sorry I missed your comment until now. Programmers worked on a simple idea of physically closing electrical contacts using sturdy (moveable) pins fixed to a slow moving wheel. The action was just the same whether driven by an impulse slave movement or a synchronous motor. A mercury switch was often provided to shorten the period when the contacts were closed to a few brief seconds. Otherwise the school bells (or other devices) would ring for a considerable time until the activating pin had passed the contacts. Often a fixed mask would be used to leave the contacts open at the weekends. There being no point in having bells ringing all over an empty school. A push button was often provided inside the secure case so that a supervisor could ring the bells continuously in the event of an emergency. (or fire drill)

tom said...

Hi, I'd just like to say thanks for spending the time to put this info up on the internet. we've owned a C7 master clock for some years now and its just been sat in our garage. i tried to get it going a few years ago but just gave up... but with this info i'm going to give it another go and install it on the thick stone wall in the house.

Thanks again,
Tom

Chrisbee said...

Hi Tom

My apologies. Yet again I have missed a comment on my blog.

Did you have any luck with your C7?

You need to feed the clock with a low DC voltage and set the current to 0.22Amps with the clock's own variable resistance unit and a multimeter.

The current is important while the exact voltage is not. 9-12 volts from a cheap, plug-type DC power supply will be a good starting point. These clocks are quite noisy so a living room may not be the best place for it.

Chris

donald said...

I have a C7 which has been exiled to the garage for being far too noisy for a domestic environment. I can live with the Synchronome in the lounge but not the C7.

To aid with mounting vertically, C7s had small brass pins set into the wood of the case, two on the edges, top and bottom, visible when the door is open and two on the left hand side of the case. These can be set to true vertical using a plumbline. They are often difficult to notice as the brass will have tarnished. Gents thought of everything.

Don

Chrisbee said...

Hi Donald

Thanks for pointing this out (about the pins). An oversight of mine which should have been mentioned and illustrated.

I can hear my own C7 master clearly through the walls of the house. I suppose one could try improving the reset damping without altering the clock's originality. One can't softly suspend the clock case without the pendulum losing energy.

Perhaps there are modern materials with very high impact damping and very low bounce. It probably just needs something better than the original thick felt.

You should hear the racket a Waiting Train movement makes when the pendulum gets a push from the electromagnets! It makes a C7 sound fully domesticated. :-)

NormanNormal said...

Hi,

Firstly thanks so much for your blog - I've just started collecting these amazing machines and it is in no small amount to do with the information which you have provided on the internet.

I have a C7 which I know how to get working, but I have some questions about my c69. It is the same as yours, but I believe that mine works off a 24v current (that's what someone has written inside the case) and the ohms on my electromagnet are much higher than yours. Is this something you have come across?

Secondly, you state that the wheel is advanced by half minute impulses - yet if I manually depress my magnet it advances by minute impulses. I wonder if you have any knowledge why that might be?

Thanks again for all the information that you have posted - I hope that you have seen the price these pieces are going for on e-bay - people are definitely aware of them and young people, like me, are rescuing them for the future.

Chrisbee said...

Hi Norman

Thanks for the kind words about my blog. I'm glad you found it useful.

I haven't heard of a one minute impulse C69 until now. A one minute impulse would require a 60 tooth ratchet wheel for the slave movement to drive. Have you tried counting the teeth?

The reason I ask is because a poorly adjusted slave mechanism might push two teeth forward instead of one. Though the high resistance coils would seem to suggest you do have a special.

Your 1 minute C69 would be an interesting subject to bring up on one of the specialist electric clock forums. Are you a member of either? If you prefer not to post yourself I could ask on your behalf.

Chris

NormanNormal said...

I have now counted them, and yes, there are only 60 teeth on the ratchet wheel.

I would be happy to share it on other forums - maybe we can exchange e-mail addresses and I could furnish you with pictures?

Chrisbee said...

Hi

I can be reached on:

chris.b (at) smilemail.dk

Chris

Keith Bartlett said...

Hi
In have just bought one of these can you tell me what the holes are for on the inside of the 24 hour clock, I know the outer holes activate the circut but for the life of me I do not know what the inner ring of holes are for..

Regards
Keith

Chris.B said...

Hello, Keith,

I have always presumed the second row is for a second set of contacts. This would allow two sets of completely independent bell programs to run at minimum expense. Though both sets at the mercy of the bell silencing contacts on the day of the week cam.

The main frame has an identical contact support bracket projecting on each side of the casting. One set of contacts would have to be external to the outer ring. The other internal so as to clear the other ring of actuating pins.

Regards
Chris

Chris.B said...

Hello again, Keith.

I just found an image online of a double contact bell programmer. However, both contacts are on the same bracket. One internal the other external. Perhaps the contacts could be duplicated on both sides of the main frame to allow 4 different programs?

https://www.worthpoint.com/worthopedia/gent-pul-syn-etic-c69-programmer-288432502

Regards
Chris

Keith Bartlett said...

Hi Chris

Thanks for this I too have just found an image with a second set of contacts mounted behind the day dial, which were activated by the inner row of holes on 24hr dial, I can only assume these activated a second operation such as turning a light on or similar. The 24 hour dial must have been a generic component which was used on different models of the timer I must have bought the cheaper model :-)
I am just in the process of getting this tested do you happen to know if the bell ringer requires a separate DC power supply?
Below is a link to the one I have bought
https://drive.google.com/file/d/1VKf8PXTYEk1ZAbOOpV5ovQVmoXtaVi0b/view?usp=sharing

Thanks Chris
Regards
keith

Chris.B said...

Hello Keith,

You have the mains driven model rather than a slave movement driven type. So you don't need a master clock to make yours work.

The only need for a DC supply would be for using the programmer's contacts for switching something at intervals. LED lights? A timed buzzer to act as an alarm clock? A school [electric] bell?

You'd need a motor driven bell *ringer* to actually strike a bell. There's a Gents one on eBay but its collection only. They are rather "lumpy" to send in the post. Though a courier service might handle it for you if you're not local to the seller.

Regards
Chris

Keith Bartlett said...

Hi Chris

Thanks for your input, I shall be looking for an old gents bell or servants bell to put on the end of it once I get it powered and working, will also need to make a case for it.
Shall let you know how it progresses.

Cheers
Keith

Chris.B said...

Hello, Keith,

Best of luck with your restoration.

Not sure if you had any pins supplied with your programmer.

If you use standard, tapered clock pins do check they don't protrude at the rear of the large pinwheel.

This will jam the mechanism and may cause damage.

Regards
Chris

Keith Bartlett said...

Hi Chris

Thanks for heads up,yes I got pins and they seem fine

Cheers
Keith

Keith Bartlett said...

Hi Chris

Update, got power to it keeps good time. As an output wired to a ornamental bonsai tree with led’s which light up when activated (wife did not want noise) going to re-varnish base and put into acrylic display case. Link to photo https://drive.google.com/open?id=1oygmAPbvJ_qWqINEvJaVI5QI2HDtW5ng

Thanks for your help

Cheers
Keith