Making a phone ring

[EightySix Four]

Is there some way I can build a box that when a phone is plugged into it, and a button is pushed, it causes the phone to ring. I am in a theatre class and it would be really useful, I see radionshack sells one but they're over 100 dollars, could I make one with a simple button for cheaper?

 

[MalikChen]

If it is a "normal" phone that does not require a power cord, you can apply a certain amount of current (45V, IIRC) through the telephone wires to the phone, and it will ring. Normally (if you're connected to a network), the system will then drop the current to a certain voltage that is below 45V but above 8V (what is being sent to the phone at all times when it is not active) when you pick it up. Only problem is, if you built one of these boxes you would have to figure out how to make the current drop when someone answered the phone. What I would suggest (being a techie in drama myself), is to have a boombox play a CD/tape of a telephone ringing, and have somebody start/stop it when appropriate.

 

[Machupo]

IIRC -48VDC is to run your phone (i.e. enough current because of line resistance to cause the local switch or NExT to give you a dialtone)

Also, IIRC, the ring is 90V, 20Hz

sorry if my brain is a bit mushy, but i've been hammering on this opteron system for the past couple hours and my brain-clutch isn't doing so hot... hah

 

[EightySix Four]

Well we do the cd playing, but the problem is it doesn't always get stopped at the appropriate time. I've seen boxes where you push the button and when they pick up the phone it goes off like normal, because the phone actually believes there was a call, and behaves as so.

 

[Machupo]

ok, so the phone onstage rings and goes off when an actor/actress picks it up?

it'd probably be easier if you just bought a battery powered bell from radio shack, popped it apart, added some wires between the phone and the switch... viola, something that sounds like a phone and can be triggered from offstage -- same problems as the CD, but less latency

i know 90v, 20Hz is what the telco uses, but if you just experiment with a phone all sorts of different voltages might work (such as battery)...

sorry that i can't be much more help

 

[Shalmanese]

why not just do what all tech crews do and manually drop the voltage back down when they see the actor/actress pick up the phone? I think phones are preferable to CD's because theres something about the shrill, directional ringing of a phone that your sound equipment just can't replicate.

 

[ScottMac]

The local loop runs at -48 (minus 48) volts DC.

The ring voltage is 90-110 VDC, 20 pulses per second (not Hertz).

Standard ring cadence is .5 second <ring> 1 second <off/no ring>

Caller ID is sent immediately before the second real ring (most CID phones delay the first ring so that CID can be transmitted). If you listen on an old POTS phone, you'll hear what sounds like a burst of static just before the second ring.


FWIW

Scott

 

[glugglug]

The ring is 90VAC (not DC).

If you cut a power cord and connect the 2 main leads to the 2 wires in a phone cord plugged into the phone, it will probably ring continuously when you plug it in. (if it doesn't blow it out cause that's 120 not 90V, but should still work...) The phone cord isn't made to take that kind of power for any length of time, however, and if you leave it plugged in for more than a few seconds it is likely to catch fire.

 

[imported_jb]

maybe something like: http://www.phreak.co.uk/fone.r...r/uk_boxes/magenta.htm or google for "magenta box"

 

[Machupo]

err, last time i checked, 20 cycles per second was 20Hz (a Hertz being defined as one cycle per second and all)... oh well

at any rate, yeah, the easiest way to do it if you can't create that sort of power (and don't want any combusting phones... useful for poltergeist or something, haha!) would probably be a prop bell...

 

[imported_jb]

or... you could plug it in.

 

[silverpig]

Or... just make it a cell phone and actually call it...

 

[Shenkoa]

"you can apply a certain amount of current (45V, IIRC)"

Current is measured in amps not volts.

 

[DrPizza]

Originally posted by: Shalmanese
why not just do what all tech crews do and manually drop the voltage back down when they see the actor/actress pick up the phone? I think phones are preferable to CD's because theres something about the shrill, directional ringing of a phone that your sound equipment just can't replicate.

I worked on a theater production last year... Why not have a recording of exactly 3 rings on the phone. If the actor/actress can't learn to pick up the phone right after the 3rd ring, then I think the timing of the phone ringing is the least of your problems.

 

[DrPizza]

Also:
1. assuming you have some set changes, simply playing the sound clip leaves far fewer possibilities of problems. What happens if wires don't get connected (or get disconnected) during a set change?

2. Since tech people sometimes screw up more often than the actors (which is why they don't end up on stage), have a back-up plan in case they screw up. ie: actor stops from normal script, answers phone and shouts "No, I don't want to change my long distance company." - adds a bit of comedy and covers for the mistake, although the more savy people in the audience will recognize it's a screw up and find humor in the actor/actresses ability to deal with it.