ginjah warrior

I have no idea about minidiscs, but I have faith in the technology and I will submit to your guidance. I want to leave a recorder outside over night (in a waterproof container) and have it record for 10mins every hour (or for 30 mins every two hours, etc). Then pick it up in the morning and find out what was making noise during the night. I want to find out whether different frog species call at different times during the night, to complement a biological survey. So basically, what should I buy? The only thing I've been able to find that does timed recordings to MD so far is a hifi deck, which is obviously of no use in a swamp!