That's how it's done:
Possible mains voltage disconnect (for 50 Hz hum)
Set to sound - red LED flashes ...
Klemen crocodile to the cable to be traced
With the receiver tip line on the wall along track ... investigate the whistle ...
or hold on veins on suspected destination ...
A high-pitched then says "Bingo" which is the desired line ...
I am thrilled at the toal renovation in an old building -'ve saved hours!
Make sure that when you turn the switch must be in the center - thereby
he may have been left inadvertently on one ..
(After a day the battery was not yet empty fortunately)