Thick film hybrids.....hmmmm...can't exactly recall but something like that for current sensing for bulb failures would have been needed..
I vaguely remember visiting a thick film hybrid manufacturer and being told they were making stuff for XJ40. I was there to source a circuit for a PBX line card in my days as an electronics engineer (before I went over to the dark side in Marketing). Hybrids were a way of both achieving the density we needed (pre surface mount directly on to PCB) and the accuracy with trim to function resistors. It all seems so long ago.
