9 Volt, Battery Powered, Telephone Intercom System 

+F1shard I did not use a resistor

+F1shard Thanks! Analog phones come in many different forms. The internally circuitry is not always the same. My friend was able to power his phone off of one battery and no resistor. Another friend of mine ripped out the dial pad and powered it with a 9V battery. You have to take a look at what you are working with internally. The resistor is supposedly there to help limit the current on some instruments. I've run into some funky analog phones before, so I guess it could be helpful to someone. In a normal analog phone, when on-hook the phone actually expects to see up to -48V. When the phone is off-hook, it usually expects between 3 to 9 volts at 30mA to 40mA. This can vary a few volts higher on some systems.

+Skinny R&D that's kind of what I was thinking. Thanks for the response. Interesting to hear others are having different results as well.

The resistor will change the sound and volume. And the ohms will affect the volume. They will also roll off bass frequency. I would really consider using one. I would try a 500k potentiometer as well. it is passive and needs no power. It increases your volume and gives you control over it. If you look up a G&L Legacy (USA) schematic. They have a all passive design with a volume, treble, and bass. It would make you much louder, and you could fine tune the sound quality.

That’s how the army did it on the TA-312 field telephone system

Yes that’s the problem

Your handsets are too close, so the phones are way too sensitive.

I think u can use them for a light, but u would have to see it when it lights up or it would have to be in a dark room.....why not just use your cell phones I mean seriously

@@achristian2851 I would do this for my kids. They don't have cell phones, seriously.

@@franklinmckenzie8856 oh ok. I didn't think of that

@@achristian2851 I am trying to find a way to do this at my camp where there is virtually no cell phone signal.

@@MrWoodchuck59 could walkie talkies work

The TA-312 field telephone

+allan egleston Cool. I'll check it out. Thanks!

Hmmmm... Perhaps try some different phones.

The technical aspects are clarified from 3:00 onwards. If it doesn't work it means you either wired it incorrectly or you are using ancient (mechanical) telephones which needed higher voltages.

Seth B Like a tone remote intercom? I use two Motorola T-1300 tone remote desk sets connected with one pair of telco cable. They work fine. No need for a ringer. While the handset is cradled the phone's internal amplified speaker is enabled.

On eBay you can buy a used "Teltone TLS-4" or "Teltone TLS-5". It has four phone jacks, dial tones, accepts pulse or tone dialing, the phones ring when you dial, you can have two conversations at a time, etc. You can assign a phone number to each line, and it even does conference calls and caller ID. It has absolutely no ability to connect to the public phone system but for an intercom system it works great. You might have to pay $150. A used PBX costs just as much, but is so complicated that it would be totally hopeless for most people. The Teltone is not too difficult. Its instructions are available as a PDF online, and it is easy to use with its default settings.