Amprobe AT-2005 and AT-2005A are no longer manufactured.

In many industrial places, hospitals and large buildings electrical circuits run in metalic conduits.  It’s a great way to protect cables, but when it comes to tracing them behind walls it might be an impediment, as such conduits tend to depress the signal.  The only way to trace wires successfully over-and-over again is by using wire tracer with signal booster.