I've got a phone system for the company I work at. We have a line in for the FM radio, it plays music for when people are on hold. What would be the easiest way for me to have the radio fade out at timed intervals (every 5 minutes say) and play from a bank of 5 or 10 short pre-recorded company related messages. Is there a software solution out there for this, or a piece of hardware i can use?
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There are many commercial solutions available for this. If you don't like any of those, there is a pretty simple way to do it.
Pick up a compressor with a side-chain input, and some sort of two-channel mixer. An Alesis 3630 and Nady MM-141 come to mind, but you can use other stuff if you want.
Record a CD with your messages, spaced however you want them. Find a CD player and put it on repeat. Your CD player outputs in stereo. Hook one channel up to the sidechain input on a compressor and the other channel to one of the inputs on the mixer.
Hook your FM radio to the input of the compressor, and the output of the compressor up to another input on the mixer.
Hook the output of the mixer to the phone's music-on-hold input.
Now, what we are going to do is compress the music from the FM radio based on whether or not audio is coming out of your CD player. The idea is that with some tweaking, the sound of the FM radio will duck out of the way when your announcement comes on. The mixer mixes both sounds together, but the FM radio will have its gain reduced down a ton, so it won't be an issue.
On your compressor, set your ratio to infinity:1, your threshold around as low as it will go. Set the release to two seconds. Give it a listen. Experiment with the compressor settings if you'd like, particularly on attack and release.
Now, you will find that the announcement bumps right up against the FM audio when it starts. A very simple way around this... on your CD, record one channel with some sort of pilot tone. 1kHz at 0dB will do. The other channel should be the announcement. The tone should start a second or so before the announcement. This essentially cues the FM radio signal to get out of the way.
Let me know if this doesn't make sense, and I will try to explain it better. Best of luck!