On Sat, 03 May 2008 18:05:47 +0100, Peter Scott wrote:

Yes I wondered about that. I thought perhaps bats used much higher
frequencies than the repellers, about 150 kHz and higher.

Depends on the species, most use bewteen 20kHz and 100kHz:

http://www.bats.org.uk/helpline/help..._bat_detectors.
asp

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Cheers
Dave.