hen select your tip-tanks one at a time. You should be able to "listen" to the valve making its way across to your selection. You should hear a definite change in the static pattern you are listening to, which of course, ends when the valve selection completes!
And if the valve doesn't select correctly, you will hear the radio very clear on one side.
There is nothing complex about the BN2 systems, the biggest catch is people getting confused between the different models. carby/non-carby, different fuel systems, different instrument layouts..
If the pilots pay attention to which they are flying, no problems... just keep there feet off the brakes when taxiing.. they get destroyed VERY quickly when this happens..