TELEPHONE

[jamiewoody]

what voltage does a basic, landline style, touch tone telephone use? i wonder if i could bend one of those like i would bend anything else, or harverst a tone generator out of one, and add other features.

[Gordonjcp]

If it's a fairly old telephone you may find it uses pretty straightforward chips inside.  Mostly the line bridge and tone generators are on a single chip, with any "clever" stuff like handsfree being other chips.

You could stick a PP3 battery across the line terminals and see if it makes a noise.  Ringing voltage is typically about 50V AC.

[jamiewoody]

nothing "clever"...just a touchtone (not rotary) phone you plug into the telephone jack in the wall. if i knew how many volts that runs on,it would help. i'm not sure how SAFE it would be to take a telephone apart then start poking around while it is plugged in.

[Gordonjcp]

As I said, a PP3 battery will power it enough for the touch tone part to make noises, but you'll need something like 50V AC for the ringer to do much.

Do not fanny about with a real BT line, they will get annoyed and possibly disconnect you.

Here's a good article:
http://www.cycom.co.uk/howto/bttelephone40macurrentsource.html

Also this:
http://www.wppltd.demon.co.uk/WPP/Wiring/UK_telephone/uk_telephone.html

The BT line sits at about 50V DC when the phone is off-hook, and drops to about 10V on-hook.

[jamiewoody]

hmm...

i think i'll forget it. unless i could figure out which part is the tone generator for the push button dial. i love the tone it makes, especially the older, '80s  models.

i'd like to just remove the tone generator and buttons and design around that. i used to like to play "marry had a little lamb" on the phone when i was a kid! lol

[Gordonjcp]

So - as I said - stick a PP3 across the line terminals and enjoy that beepy DTMF goodness!

[jamiewoody]

is a PP3 a battery pack for a cordless phone? and if it is not cordless, i assume it will still work?

[Gordonjcp]

A PP3 is one of those little square 9V batteries that you get in smoke detectors, and not much else these days ;-)

[Circuitbenders]

In my experience you never get them in smoke detectors, because they've all been stolen to power some guitar pedal in an emergency 

[jamiewoody]

well, if  it is 9v, then i will somehow rig up a standard 9v.