Control Group Blog

Control Group has rolled out a number of Call Manager Express systems for our clients, and one issue that frequently comes up is what to do with callers on hold. While most companies – ours included – work to avoid putting people on hold, it does happen. The easy options offered by the Call Manager Express are a double beep at regular intervals or a ‘Music on Hold’ file that you can store in the host router’s flash memory. I have received many complaints about the beeps and even a single repeating music file can be insufficient for some users.

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.

One of the unique things about how Control Group works is that our focus is much more involved than simply putting in a solution for a client and then moving on. We work with our clients to determine how they work, so we can design IT solutions that really fit their needs. Since we have partnerships with a variety of vendors, we work with our clients to arrive at the best solutions for their business. This means we do quite a bit of research and planning before we begin a project — and then a great deal of testing during and after we install new hardware or software.

I do some work on implementing storage systems for our clients, and we’ve found that different applications have different storage requirements. For example a video post production facility — like the facility at WWE — generally needs lots of disk space that is very good at reading and writing large files at high speeds. The storage here needs to provide good streaming throughput, because high quality video files generally have high bit rates, and are being stored or played back from the disk in real-time for ingesting, editing, or playout. If the storage system is not fast enough to read or write the file in real-time, frames will be dropped. This can cause unsatisfactory media files, programs to crash, or audio and video to become out of sync.

10,000 RPM SAS disks. That's some serious storage.

Suboptimal read/write performance can become a huge problem. When we put in a new system this is something we need to test. I usually do the test with a tool called lmdd.

lmdd comes from the lmbench tools which are provided by Bitmover for benchmarking systems. lmdd is great for testing streaming bandwidth. In most of our engagements with video, we install a Stornext or Xsan filesystem so we’ll run our tests against this. lmdd will probably work on any filesystem that you can mount on your Mac or Linux computer (Leave a comment if you need a version for Mac OS X, I have one compiled).  lmdd lets us verify exactly what the maximum number of megabytes per second we can push through the storage and point us to where we need to make changes to the hardware or software configuration. I use lmdd like this :

lmdd of=/path/to/test_file count=1g

lmdd if=/path/to/test_file

The first tests write performance and the second tests read performance. More information about the syntax is available in the manual page for lmdd. The results of the command from a server I was testing looked like this:

2147.4755 MB in 6.8003 secs, 315.7914 MB/sec

lmdd is great because it’s easy to read. This result shows I could write to the filesystem at 315 megabytes per second. That’s really fast! This is from a test with a server with a lot of RAM and a special filesystem that took advantage of that cache. When I run it on my Macbook, I get a result like this:

18342.6171 MB in 376.7685 secs, 48.6841 MB/sec

So the next time you’re interested in how your storage is performing give lmdd a shot and let me know how it goes. If you’re looking for more information about storage performance testing then stay tuned; I’ll be posting about testing storage with tools that benchmark small reads and writes next.

Apple’s venerable Apple Software Restore (asr) tool includes the insanely useful ability to image a nearly unlimited number of network clients. It accomplishes this via a router’s ability to broadcast data to any number of clients simultaneously from a single IP address. Known as multicasting, this allows even a modest computer to image a hundred Macs with 35GB images in a single fell swoop.

An ASR Restore Image in Disk Utility

The disk images asr works with are the same format used by Mac OS X’s Disk Utility. This means you can do a rollout over the network and keep the master file on hand in your re-imaging kit, should one of your workstations run into trouble and need to be re-imaged over FireWire. To ensure the sanctity of the final result, disk images include an embedded checksum which is automatically verified during the deployment process. This can be a significant advantage in using asr over of Apple NetInstall, which requires its own folder-based setup of restore source files.

Disk images are also hardware agnostic for the most part. You can build your image on a Mac Mini and apply it to anything from a PowerMac G5, to an Macbook Pro so long as it can get on the same subnet as the asr host.

The usual caveats of disk imaging apply unfortunately. You’re going to have to sweat individual serial numbers if you don’t employ network or volume licensing. Settings like hostnames and non-ubiquitous local users will require individual workstation visits without centralized management. However, having asr around to do the heavy lifting means you may be able to turn a strenuous two day deployment into a breezy one day affair.