I could really use some help 
At work they have some custom built intercom boxes they use all over the place. The problem I have is that there are a fair number of people still using some 'telephone' style intercoms that I think were made by Motorola.
I know very little about the systems themselves but I know the problem it causes!
Depending on how much wire is connecting the various boxes, there is almost always a whining feedback in the background when someone keys a Motorola box. Many times though, is the real problem. When they key there is a horrible 'chirp' every time they press the transmit button. If the custom box is turned up loud enough to hear people talking, this chirp is hideously loud.
The system is connected with simple 'slash wire' which is probably about 18-20 gauge stranded stainless steel and might be 20' long or 300'. They connect with dual banana plugs.
What I'm looking for is help building a simple, inexpensive (I hope!) low pass filter that could be mounted on another dual banana plug so I can move it around when I move from place to place. I'm thinking a cutoff frequency of maybe 500-1000 Hz (since it's only for voice... not music), maybe even a little lower. Ideally, I need to keep the price down since if I can find something that works, I suspect these things will be in demand!
At work they have some custom built intercom boxes they use all over the place. The problem I have is that there are a fair number of people still using some 'telephone' style intercoms that I think were made by Motorola.
I know very little about the systems themselves but I know the problem it causes!
Depending on how much wire is connecting the various boxes, there is almost always a whining feedback in the background when someone keys a Motorola box. Many times though, is the real problem. When they key there is a horrible 'chirp' every time they press the transmit button. If the custom box is turned up loud enough to hear people talking, this chirp is hideously loud.
The system is connected with simple 'slash wire' which is probably about 18-20 gauge stranded stainless steel and might be 20' long or 300'. They connect with dual banana plugs.
What I'm looking for is help building a simple, inexpensive (I hope!) low pass filter that could be mounted on another dual banana plug so I can move it around when I move from place to place. I'm thinking a cutoff frequency of maybe 500-1000 Hz (since it's only for voice... not music), maybe even a little lower. Ideally, I need to keep the price down since if I can find something that works, I suspect these things will be in demand!
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