Home to garage landline

>>1147122
They're called intercoms.

use four wire phone line for the circuit
put a 9v battery in series in the 'loop' using the red/green wires
hook a buzzer and switch on the black/yellow pair

phones are amazingly simple but deceptively complicated
what you want to do can be done but requires special voltages and frequencies for the 'ring' signal (90vac at 20Hz)
this signal is sent over the same pair as the voice line which is normally 48vdc
you'd also need sensor to detect when a receiver was 'off hook' so it would ring and sense when both were off hook to know to stop the ring
there are devices available for this but not at /diy/ prices

>>1147128

I understand there are dedicated intercom devices, but I'd like to repurpose existing telephones.

>>1147151

Interesting, thanks for the information! "/DIY/ prices" aside, what are the devices available called? What's the term for the specific function I'm looking for?

>>1147122
http://www.epanorama.net/documents/telecom/telephone_intercom.html

Has a good alternative to making a ring generator

>>1147155
>what are the devices available called?
Telephone Line Simulator
or
Telephone Exchange Simulator
They come in a variety of features and prices.

Walkie taklies

>>1147122
It may be cheaper to reuse the phone wiring with an intercom type device than trying to reuse the actual phones too

It's tough, but sometimes you have to get rid of old junk instead of spending hours and tons of money on devices and adapters to reuse it.

>>1147191
This was the shit in the 80s 90s electrical hobbyist.

It was in the back of every other issue of popular science or Run! Magazine ot whatever.

Phones need 'battery' to work which is 25-35ma and you may as well keep it nicely regulated.

To make it ring though you need a ring generator circuit which is still easily possible, but is more advanced. You would end up with a push button next to each phone to ring the line.

>>1147122
used to see this done with army surplus field telephones. crank to ring.

Google ringdown circuit, Viking electronics has everything you will need. Had the old school inside the house phone guy install three "red phones" at work. 2 direct call a cell number and 1 direct calls an intercom extension.

>>1147122
You need to paint the phones red!

File: acc6a0ee44b39aef4079a66c3373.jpg (20KB, 400x224px) Image search: [Google]

20KB, 400x224px

To make the other phone ring you need to send an alternating current down the line on top of the direct current that you get in the network. When a phone rings, its because it receives this alternating current signal from the network. An electric bell will ring only on alternating current, and that's how it worked in older phones.

I collect old phones, and I connected pic related up in my house. It is what was called a "local battery" phone - so it needs its own direct current supply so someone on the other end can actually hear you. It has a hand cranked permanent magnet alternator, which sends the AC signal. I turn the crank, all the phones in the house ring, simple as that.

So, what you need is either an alternator, or a circuit with a transformer connected to the AC mains, lowering the voltage to about 60V or less, activated with a switch, connected directly into your home land line. Technically, you need to also lower the frequency to 20Hz, but this is more difficult to do, and old phones with actual bells will ring either way.

>>1148098
>and old phones with actual bells will ring either way.
SOME old phones with actual bell will ring either way.
Many old phone ringers are 'tuned' to not respond to signals outside of a 17-35Hz band.
Newer phones with electronic ringers will ring with 20-60Hz signal.

>>1147128
it's called yelling

>>1147122
I'd just buy a cheap key system like a Panasonic 824 and program it to do what you want. You'll get lots more features and the ability to add more phones around the house too.

>>1147122
Yeah i imagine a cheao intercom system would work as good or better for the price of your phones.

Bonus points for wireless.

Truck stoos run solid sailes on the cobra 29 ltd. U may not even need an antenea bit if u get the kit and mount the anteneas in line of site and low to keeo from interception it should be crystal clear. Most have call bees or u can key uo and just holler.

Buy one of these
http://www.vikingproductstore.com/viking/security-equipment-21398-Viking_DLE200B_Two_Way_Phone_Line_Simulator_DLE200B.html

Plug it into wall, phone cords into both ends.

Lift one phone, other rings.
When answered, two way call..