On Wednesday, 1 January 2014 15:42:34 UTC, wrote:
I have purchased a second-hand Standard C510 hand portable. It has a fault; as soon as it powers up, it gives 4 rising pitch tones, and permanently transmits, and displays 433.00MHz. None of the buttons do anything, apart from giving DTMF. All I can achieve is to switch it off again. Does anyone have any ideas if it's in a weird mode, or how to fix this?

The C510 had a problem with it's rubber buttons sticking on, could be one is
stuck on causing a switch on fault.
Dismantle the radio and clean the back if the rubber key pad with non lubricating cleaning fluid