I need to feed a mixing board to a Azden 10BT body-pack transmitter. Can I get the monitor out or headphone out? Just don't want to damge the transmitter. Dan.

Sure.

You want to be sure that the mixer output is at microphone level, which is what the bodypack is expecting to see at it's input. Mixers will often be switchable at the output. If all the mixer will output is LINE LEVEL, then that WILL overdrive the bodypack unless it has some kind of trim control on it's input circuit.

The simple and expensive solution is to use an "in line pad" from a catalog like Markertek or TecNec that will drop a line level to mic level - then just feed that properly diminished signal to your transmitter with an XLR to whatever the bodypack wants adaptor.

OOps, typo - that's simple and INexpensive solution...

How much attenuation? I see M-audio sells a 10dB pad with 1/8" plug for their MicroTrack. Is there a standardized difference between line level and mic level?

There are specs for what standard line level and mic level are supposed to be but many manufacturers don't quite follow them

There are a couple of different versions of line level.
With my Lectrosonics transmitters I use a 50db pad to pull down line to mic.
10db is really just for fine tuning the different line levels not pulling it down to mic level.

Take a look at either of these Atteuator Pads.

Audio Technica AT8202
http://www.bhphotovideo.com/bnh/controller/home?O=Search&A=details&Q=&sku=68085&is=REG&addedTroughType=search

or the

Rolls DB Matchbox
http://www.bhphotovideo.com/bnh/controller/home?O=Search&A=details&Q=&sku=155416&is=REG&addedTroughType=search

Both should pad your signal very well, and are very easy to use. I would pad your signal to 30-40db most likely.

From my experience, in most situations where a mixer is used they don't output a very hot level. Especially in PA situations where the master output level is used to control the loudness of the PA. If you are controlling the mixer yourself or if you can get a feed before the master fader and the mics are all properly gained then a -50db pad would work well. However, if that's not the case, you'll be cutting down the signal way too much. I tend to use an adjustable pad with -10db, -15db and -20db attenuators. That generally does the trick. I also have a Rolls Matchbox that I occasionally use when I need more attenuation.