I didn't chime in earlier because I didn't feel that the OP gave enough specific info. Was it to time delay on an actual loss of control power or a switching, things like that. Although I've dealt with a few of the expensive pneumatic bleed delay release Agastats, I've never designed around one. You shouldn't have to. The ladder that you're sensing loss of power on won't have power, but the circuit that you're controlling must. So just use a simple, cost effective, Time Delay Operate relay on your controlled circuit. Drive it with a NCHO (normally closed, held open) contact of a POK (Power OK) relay. If you want to switch back immediately, POK is just a standard control relay with its coil across the ladder. If you want to delay switching back, just use another TDO as the POK relay. A little thought on the design will let you buy a box of suitable relays for the price of that special Agastat.
Joe
