When I started searching for a way to connect an audio feed to a gateway router, I found that there were no great turnkey solutions. What I did find is that there is a way to make use of an available FXO port to bring a live feed into the system with some inexpensive parts. The solution I have deployed requires a surface mount RJ 45, a chassis mount RCA jack, and a stereo 1/8″ mini to RCA adaptor. All of these pieces can be found at a nearby electronics parts store and purchased for under $20. The FXO port and an iPod will set you back some but if you want easy control of your hold music it may be worth it.

Build the Adaptor

To make the adaptor, open up the surface mount box and figure out how you will attach the RCA jack. In one case I used a drill bit to make a hole for it, in another case I found a form factor where the notch for a cat 5 cable fit the connector perfectly. You may also find a general purpose surface mount with modular fittings where an RCA “snap in” would snap right in.

Once you’ve sorted that you will need a pair of wires from either a solid or stranded piece of cat 5. Punch these down to pins 4 and 5 of the RJ45 and solder the other side to the RCA jack.

When you are done it should look like this.

Adaptor wiring detail. Though the jack in this configuration is an RJ 45 you can use a standard RJ11 phone cord to connect between the adaptor and the FXO port.

Configuring the Voice Gateway

Configuring the voice gateway is pretty straightforward:

1. Create a DN for the MOH call out with an unused multicast address

ephone-dn 274
number 1 no-reg primary
moh ip 239.12.13.1 port 2000 out-call 899

2. Configure the available FXO port remain open to the iPod

voice-port 0/3/3
signal loopStart live-feed
input gain 2
description To MoH Live Feed

3. Create a dial peer to connect to the FXO port

dial-peer voice 55 pots
destination-pattern 899
port 0/3/3

4. Configure CME to use the multicast for MOH

telephony-service
multicast moh 239.12.13.1 port 2000

Then Shut/No shut the voice port to invoke the change.

I have been using one of the built in USB ports on our gateway here at Control Group to power the iPod which turns out to be very convenient.

Safety and Other Considerations

There are some very important caveats.

1. The adaptor I describe is potentially dangerous. If you were to connect an iPod to a POTS line or an FXS port feeding a battery signal you could damage the iPod or the device connected to it. You could also receive a serious electrical shock.
2. The use of copyrighted material for Music on Hold can be a violation of the rights of the copyright owner.
3. The adaptor will only work with one channel of audio from the iPod. If you use a mono 1/8″ to RCA cable it will short out the other channel.

These issues need to be minded if you would consider this solution. Also, keep in mind that people’s taste in music varies widely. Implement Music on Hold and you will find out just how much!

Miles Green is a Senior Network Engineer at Control Group and worked as a Musician and Recording Engineer in a previous life.