spannersatcx, thanks for the input.
Is all of the above an actual observation or did you take it from a maintenance manual or similar?
Either way, I bet it refers to the old SDCU, as from my understanding with the new SDF unit you have to hold the PTT pressed in, to get all the above effects (but the test is also quicker). If you have a chance to find out, can you please let me know the unit type? One way to tell is to look at the reset breaker in the very top right corner of the RESET panel (261VU, I believe), whether it reads SDCU or SDF.
Cheers!