Making a phone ring - Community Theatre

[TelePlay]

This simple circuit, with the proper value resistors R1 and R2, would open and close a relay with a 7 volt DC coil and a 120 VAC SPST switch (instead of the diode light D1), to switch the ringer power coming out of a Tellabs ring generator, at 2 second/4 second cycle.

The 9 volt power source that drives the timing circuit drops a volt or two at pin 3 so a lower voltage/current relay coil would work.

A simple toggle switch in the one of the Tellabs two wires would allow one to start the phone ringing and stop the ringer power when the phone is picked up.

http://www.555-timer-circuits.com/flashing-led.html

[TelePlay]

An astable or oscillating 555 timer circuit using two 6.2 K Ohm resistors and a 470 Microfarad capacitor will produce a 2 second/4 second cycle.

A 555 calculator, circuit and helpful pin info are at this link.

http://www.bowdenshobbycircuits.info/555.htm

Plug in 6.2 for the resistors and 470 for the capacitor and it shows 4 and 2 seconds in milliseconds.

A 9 volt source would result in a 7.3 volt output at 200 milliamps on pin 3, more than sufficient to drive a Radio Shack SPDT relay to switch a Tellabs unit.

Unlike depending on a stagehand to make the phone ring the same each time with a magneto or a door bell button to manually switch a Tellabs generator ring  signal to a phone, this circuit would produce an exact perfect ring each time used. Something that would not distract an audience if ringing a phone many times during a play.

That's been my experience, anyway, and directors don't like distractions.

[winkydink]

An astable or oscillating 555 timer circuit using two 6.2 K Ohm resistors and a 470 Microfarad capacitor will produce a 2 second/4 second cycle.

A 555 calculator, circuit and helpful pin info are at this link.

http://www.bowdenshobbycircuits.info/555.htm

Plug in 6.2 for the resistors and 470 for the capacitor and it shows 4 and 2 seconds in milliseconds.

A 9 volt source would result in a 7.3 volt output at 200 milliamps on pin 3, more than sufficient to drive a Radio Shack SPDT relay to switch a Tellabs unit.

Unlike depending on a stagehand to make the phone ring the same each time with a magneto or a door bell button to manually switch a Tellabs generator ring  signal to a phone, this circuit would produce an exact perfect ring each time used. Something that would not distract an audience if ringing a phone many times during a play.

That's been my experience, anyway, and directors don't like distractions.

I really appreciate this info.  And I would like to give it a try.

I am not a electronics person at all so I am really going to need step by step spoon fed instructions to make all this work.

Lets say that I build this 555 timer circuit with two 6.2 K ohm resistors and a 470 mF capacitor, and I also have

- Tellabs unit
- a 302 phone with ringer
- telephone or other wire

How do I hook it all up ?  What wires attach to what ?  How does it turn on/off .  Sorry for asking so many questions but this is out of my comfort zone [I can take a phone apart and put it back together but have not done anything like this]

If someone can give me a watered down version so I can comprehend this I would really appreciate it.

[TelePlay]

I just realized this circuit would ring the phone for 4 seconds and then provide 2 seconds of no ring, just the opposite of what would be desired.

It would work only if the circuit would be turned on 4 seconds before the desired ring point.  Not the best for theater but with a good stage manager paying attention to the book, it could work, be close enough.

However, this circuit would work with a 2 second ring with 2 seconds of silence, something at is often used on TV and in movies because the 4 second pause period is a long time when on stage or on camera.

If so, a 1.1 K Ohm resistor for R1 and a 26 K Ohm resistor for R2 along with a 110 uF capacitor will provide a 2 seconds ring and 2 second pause. If that is acceptable, the following layout could be used. The phone would ring for 2 seconds as soon as the 555 circuit would be powered up by closing the toggle switch between the transformer and the 555 circuit. You would have to use several resistors and capacitors to get the desired values of 26 K Ohms and 110 uF capacitance.

This is a further explanation of the circuit layout if 2 seconds on and 2 seconds off is acceptable.

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Here's a quick sketch of the layout. I would put a SPST toggle switch in the power supply line before the 555 circuit so that when power is applied, the switch closed, the circuit begins with a full 2 second ring.

The relay needs to be a 6 VDC coil that draws less than 200 mA and the SPDT relay switch needs to handle several amps at greater than 90 VAC. I have one if you can't find any. Radio Shack has one but they are currently out of stock. The ones I have are 6 Volt Coils rated at 60 mA and have a 10A / 125V SPDT.

One line of the Tellabs output would go to the phone, the other to the relay SPDT. Use the terminals that are normally open so that when the circuit is not powered, the relay switch is open - the phone does not ring. As soon as the circuit is powered by closing the toggle switch on, the relay SPDT normally open contacts will close for 2 seconds and then open for 4 seconds. The Normally Closed pin on the relay SPDT will not be used.

Pin 3 of the 555 chip is the positive output of the circuit and would go to one of the two coil pins on the relay. The other coil pin would be connected to ground.

Don't forget the 0.1uF capacitor between pins 5 and 1 to keep the circuit from acting erratic.

The voltage out of Pin 3 is 1.7 volts less than the voltage into the 555 circuit. So, with a 6 VDC coil relay, the supply voltage transformer would need to provide at least 7.7 volts. A 9 VDC supply should work. You can always drop down the 9 VDC with an appropriate value resistor before the toggle switch. I found that my local Science & Surplus store was a multitude of transformers, they just needed to be check with a Volt Meter at the store to verify the output voltage.

I don't think I missed anything but those on this forum that have a greater knowledge of electricity and circuits than I do may have suggestions. I built this and it worked well for a half second on and a half second off. I put 2 toggle switches in my circuit. One to turn on the circuit (the relay would start to click) and the other to turn on the lamp power going through the relay SPDT. I did that so I could use a third toggle switch to short the lamp I was flashing go full on when the phone was picked up. All you need to do when the phone is picked up is turn off the toggle switch powering the circuit and the relay will go to its Normally Open position, and stop the ringing supply to the phone.

The wire from the SPDT relay out and the other wire from the Tellabs supply would go to L1 and L2 on 101A coil in a 302.

[TelePlay]

Now that I did all that work, I'm going to build one myself for my theater to use when I don't set up a Teltone POTS.

I'll be able to plug the transformer into a light board outlet on stage and leave the toggle switch on. That way the light board operator will be able to control the circuit. Off to Radio Shack for small bread board and a project box.

[DavePEI]

I just realized this circuit would ring the phone for 4 seconds and then provide 2 seconds of no ring, just the opposite of what would be desired.

Connect to the other pair of relay contacts (nc) - that will flip it back to what you want...

D.

[TelePlay]

I just realized this circuit would ring the phone for 4 seconds and then provide 2 seconds of no ring, just the opposite of what would be desired.

Connect to the other pair of relay contacts (nc) - that will flip it back to what you want...

D.

Thought about that but wouldn't that mean the phone would ring constantly until the 555 circuit was powered up? If so, another switch would have to be thrown in the layout to turn on the the Tellabs ringer supply within 0 to 4 seconds after the 555 circuit is powered up, right?  Using the relay NC pair would reverse the 4 second - 2 second cadence but not without switching the Tellabs supply, right?

[twocvbloke]

Could you not add another relay that is activated when the tech. hits the button to ring to act as a cutoff switch between the ring generator and the first relay?

[TelePlay]

Could you not add another relay that is activated when the tech. hits the button to ring to act as a cutoff switch between the ring generator and the first relay?

Yes, that would work, but again, the 555 circuit would have to be turned on 4 seconds before the first ring would be heard. From the time the toggle switch to power the 555 circuit is turned on, the ring cadence would be first a 4 second pause, then a 2 second ring, a 4 second pause, a 2 second ring, etc. until the handset was lifted at which time the phone would stop ringing and the 555 circuit toggle switch would be manually turned off.

The layout would require two (2) 6 VDC relays with a coil rating of less than 200 mA and the SPDT relay switch would have to be rated at 120 VAC and more than 3 amps. Here is a link to suitable relay with a 60 mA coil, or 10 of them, and at that price it's a very good deal considering what Radio Shack would charge if they had them.

http://www.ebay.com/itm/190605375485

The first relay coil would be turned on by the toggle switch and would close the circuit from the Tellabs unit to the second relay. Closing the toggle switch would also close the Normally Open switch on the second relay for 4 seconds opening the circuit from the Tellabs unit to the phone. After 4 seconds, pin 3 would drop voltage to zero causing Relay 2 to change to the Normally Closed position for 2 seconds causing the phone to ring, for two seconds. After that, Relay 2 would be activated opening the Tellabs circuit to the phone causing it to pause ringing for 4 seconds.

The layout using 2 relays is below. Relay 1 is driven directly off of the transformer voltage and Relay 2 is driven off of the voltage supplied by pin 3 of the 555 IC.

Since I haven't built one of these, the only problem I see is a slight tinkle of the phone should the first relay close before the second relay opens. I suppose that could be fixed with a small resistor on the second relay slowing down the voltage causing the second relay to operate a fraction of a second after the first relay. Just the difference in voltages using the direct transformer power on Relay 1 and 1.7 volts less from Pin 3 might solve this problem. Don't know. Will have to breadboard this on the weekend to see what happens.

(Additional thought, it might be as simple as switching the coil supply from Relay 1 to the 555 Pin 3 and using the transformer supply to drive the coil on Relay 2).

[DavePEI]

As far as that goes, just a push-button could be used from the Tellabs with the cadence controlled by the person pushing the button. Its all you would need.

Or, if you wanted to be fancier, do what I do with my Strowger demos - use the interruptor off a 1A2 KSU - these usually run off 10VAC. so you need also a 10 VAC supply. Use the correct set of contacts, and your ringing will be automatic. Just put its contacts in the line from the Tellabs to the phone.

Still, the simplest way is a push-button, with the operator pushing it to time the ring.

Dave

[TelePlay]

As far as that goes, just a push-button could be used from the Tellabs with the cadence controlled by the person pushing the button. Its all you would need.

Or, if you wanted to be fancier, do what I do with my Strowger demos - use the interruptor off a 1A2 KSU - these usually run off 10VAC. so you need also a 10 VAC supply. Use the correct set of contacts, and your ringing will be automatic. Just put its contacts in the line from the Tellabs to the phone.

Still, the simplest way is a push-button, with the operator pushing it to time the ring.

Dave

Yes, Dave, that would be the easiest. And instead of using a manually operated push button, a SPDT relay with a 120 VAC coil or a low voltage coil and a transformer hooked directly to a lighting board outlet on stage and the relay switch rated at 120 VAC and 10 Amps could then use a programmable light board to activate the relay to ring the phone. That would provide a perfect and exact ring cadence. Simply hook one line of the Tellabs supply across the Normally Open relay terminals and the light board would close that switch by simply powering the relay coil, as I first said in my post on August 8th. A 2 second on, 4 second off cycle run by a programmable light board would take operator error out of the equation and trust me, given a back stage person to push anything, including a simple door bell just once, will be inconsistent for several reasons.

That would be the same with an interrupter. Does an interrupter reset itself so that the first time it completes the circuit to ring a phone, the first ring is a full 2 seconds? Can you provide a circuit/layout of how an interrupter would work with a Tellabls unit?

[poplar1]

The interrupter used for ringing in 1A2 is 1 second on, 3 seconds off. I believe it returns to "home position" no matter when the start lead is removed.

[DavePEI]

That would be the same with an interrupter. Does an interrupter reset itself so that the first time it completes the circuit to ring a phone, the first ring is a full 2 seconds? Can you provide a circuit/layout of how an interrupter would work with a Tellabls unit?

An interruptor doesn't reset, just as the old motor driven interruptors in exchanges didn't. therefor the first ring can be a short one, or you can wind up with a short delay before the first ring. So really, you are getting a realistic ring. The shaft stops rotating where it does, and when restarted continues on from that point. However, as I pointed out, this is period realistic - old exchange motor interruptors were the same. Once started all rings will have the same timing as it rotates.

Wiring would depend up on the interruptor chosen - they have different pin arrangements and contact arrangements. However, you can see the contacts and chose accordingly for the correct timing. They run off a 10 volt sychronous motor (timer motor) and require quite low current to run. A 9-11 VAC wall wart works fine.

Just remember you need the 10 vac for the motor, and a pair of leads to the correct contacts inside. They work by a revolving drum with a eccentric on it which opens the contact.

Dave

[rdelius]

It would be wise to put a diode across the relay coils so when the coil is turned off, there wont be a voltage spike to kill the chip
Robby

[poplar1]

It's been 20 years or so since I worked on 1A2 but I seem to recall the motor keeps running once A and A1 are shorted to indicate an answered call, but the flashing lamp and ringing stop because they are overridden by the A/A1 answer leads being shorted. If the motor simply followed the ringing then the lights would stop flashing during the silent interval.

In any case, the ring cycle is not 2 seconds ring followed by 4 seconds silence.