Geeky electronics Q

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
I'm sure somebody here can help me find a solution.
This is part of a larger project but I don't feel like explaining it all...
Lets just say that I need to be able to hook up the audio in/out of a video server to a home phone line. Not so it can make calls, network or anything, but just to be able to use the phone line to lo get to a speaker/mic that is part of a seperate box unit that uses the line. The server just has an audio out and in to use. This is in essence adding it like if you just plug in a phone handest into the wall w/o the base unit (old-school phones anyway).

What seems to make this complicated is two things.
1, phone just uses the 2 wires for both talk and recive, and they are powered, albeit low voltage.
2, when the phone "rings" it sends out a nice huge voltage spike. I'd think that if plugged directly into an audio/mic line this would be a problem (fried?).

Any ideas on how to do this. A cool adapter, some small gizmo device, etc. It seems like a very easy thing to do but I'm having a mental block.
 
definitely unhook dial tone or the 58 (normal on a POTS line) volts will fry your electronics
 
Have you thought about adding a simple old fashion modem to the server? Then you could look up some of the standard Hayes type modem commands, to pickup, send signals etc.. The older card support standard cmd line type functions.. and there are tons of manuals online..

I have a few older modems id be happy to give ya if you wanted one...

-mike

btw: its -48v dc on the line at 'idle' and higher during a ring...
 
Are you trying to record telephone audio, or just use the telephone lines to connect to a remote microphone?

Something like this will allow you patch the telephone audio.
 
saf-t scissors said:
Are you trying to record telephone audio, or just use the telephone lines to connect to a remote microphone?

Something like this will allow you patch the telephone audio.
Click to expand...

No, don't need to record or anything. Just tapping in to talk/listen over the phone line. But wondering if that wil ldo the trick.

OK, here's a little more info if it helps. The "remote speaker/mic" I speak of is a driveway gate controller box that has the intercom/mic etc in it. It's connected to the house via phone line. When somebody pushes the button, it starts a "call" to the house. You pick up the phone and talk to them. "Go Away" or "Ok FINE you brought the beer, so I'll let you in". I can only assume its a "special" ring so you know its the gate.
To be extra cool, there's a network video server.. connected to a camera etc.. so you can see 'em from any PC on the system... and even check it out from anywhere (AKA at work).
The vid server has audio in/out. That is where this issue comes up. Ideally I want to get this in/out integrated w/ the phone line, and hence into the controller box... so that you can sit at said PC and TALK to the person.

The less elegant solution (and what I'm stuck with now) is a seperate speaker/mic for the vid server. Yuck.
 
RatLabGuy said:
The "remote speaker/mic" I speak of is a driveway gate controller box that has the intercom/mic etc in it. It's connected to the house via phone line.
Click to expand...

Your sure it's meant to interface with the POTS wiring and not simply an RJ7 plug meant to connect to *another* such "intercom" on the inside?
 
Caver Dave said:
Your sure it's meant to interface with the POTS wiring and not simply an RJ7 plug meant to connect to *another* such "intercom" on the inside?
Click to expand...

Yes. It connects to the home phone line. It initiates a 90 volt spike just like a "ring" signal from anywhere else.
 
Okay after talking to the guy's project this is (no, not my house, I can't afford a gate...), there are some potential downsides w/ tapping into the phone line.
So, trying a different route, such as literally using a seperate line from the vid server and sing/tapping directly into the mic/speaker that are in the above-mentioned gate controller box. This keeps it as essentiall ya seperate system, just sharing the speaker.
Problem here is 2 (mildly) amplified signal going into 1 speaker... how do you keep the power/juice from one from flowing back into the other source and harming it? We're only talking a few Watts max here.
Seems it'd need an anti-drawback(?) circuit of some kind, to ensure current flows only out and not back. What would you call this? I'd think it woudl be a very simple device. And am I corect in assuming this only a problem for speaker not mic, which is an incoming signal that could just be "split" to each receiver.
Remmeber, physical switch/input selector box not an option as thsi is al lremote controlled.
 
A simple radio shack diode would solve your bi-directional backfeeding issue, but Im not sure that is gouing to solve all your problems.

Ive installed MANY driveway alarm/ gate call/ and desk call systems. AIPHONE integrated audio/video etc. generally they are sold as a system and will work at oddball voltages and in some cases off the wall AC frequencies to ensure that you use all their components.

Not saying you couldnt MacGyver a half system into a working unit (if that is what you are trying) but not sure it would be worth it or survive in the long run.

PM some specifics and let me dig upome cut sheets, Ill be glad to help back engineer if I can.
 
Well I assume that the system rings you home phone just like your phon ecompany does.
Som one sugesssted using A Diode to block the dc voltage. That will not work. It will block the DC but it will also block the positve cycle of the audio wave form. what you need it to use a large capacitor that will pass the audio range of frequencys and block the DC. the you will have to get the audiio signal ajusted to to th righ level to input in your pc
 
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