TTN
I remember that NBS trainer at Lindholme well Ian. Spent many a happy hour in there bombing fictional Russian targets with names which if you looked carefully you discovered were based on past and existing staff members.
I never saw it working.
Lindholme was my 1st posting from Boy's Service and we were deliberately moved around to broaden our experience.
I started in ARSF, then I went to the 'Bombing School', where I looked after the Gee-H trainers, and the 'bench sets' in the classrooms, my mate did the H2S Mk4 ones. When we did the monthly calibrations, we each played the pilot to the other one's nav. If we didn't make a dead hit, we re-calibrated. We were probably the 2 best 'trainer bomb aimer's at BCBS. It would have been interesting to try it for real on a Lincoln.
When the EMI guys arrived to install the NBS kit we were 'assisting' them.
The biggest part was a device with 2 negatives about 4' x 4' where light was projected through to a sensor, this simulated the radar signal. The light source/sensor moved around on a 'crab'. We called the whole thing the 'fish fryer'. I dunno if the name stuck.
I was then re-assigned to one of the squadrons to get some a/c time in before going back to Yatesbury for my fitters course. I never saw NBS again 'till I was posted to 214 in 1959.