Greg,
I predict great profits for the first person to duct tape 100 'tracer tone-generators' into a 23 inch rack with 48v DC power source.
Not *quite* sure what you mean here, but you only need one tone generator - all the rest can be done with passive components. See (for instance) how tones were generated in the days of mechanical exchanges (*not* one oscillator per line) I thought about this a bit later, and realised that on ADSL (at least) it would be worth looking at the CPE. This is busy generating a linecoding with nothing in the sub 8kHz range. At the other end, anything sub 8kHz is dropped. Getting the CPE (via firmware, or internally) to stick some tone on the line would be trivial. Of course you'd need it as a configurable option in case someone wanted to use it for voice too. -- Alex Bligh Personal Capacity