Telephoning Fish is Small farm pond.

Hello, I have a question regarding telephoning fish/electrofishing. I
have a small, 2 acre farm pond that I want to survey the sizes of the
bream and bass populations in. I understand that electrofishing stuns
fish by pulses of current, but I don't know what type of phone is
needed.

I've been told a 70s vintage rotary phone will work, but also told a
40s era crank phone is required. An army field phone as also been
mentioned. Can someone please help me understand what type of phone
is needed to get the pulsed current I need for electrofishing.

Thanks.
Dave