During circuit traiining on Wirraways at Point Cook in the early 1950's, we were taught to momentarily throttle back to idle on the downwind leg and the undercarriage warning horn would sound quite loudly. Once we heard that sound indicating the undercarriage warning was operating correctly, we would apply power again and select undercarriage down. With several Wirraways in the circuit the sound to spectators on the ground would sound like 'blipping' of engines like the old WW1 biplanes.