The Beam and Calculations...

The aircraft flew a "beam" and if it deviated from the centre the pilot received dots on one side (I think it was the LH side) a continuous note- like an oboe, hence its name- if it was on the beam and a series of dashes on the other side.

Remembering her work with OBOE

After the calculations had been completed the controller agreed his with the 1/C watch and this was done for all the targets 1-4 being the usual for each site although obviously these were not ops every night. The mechs were doing per-op checks.

If the ops were in the early morning the targets were set up immediately but were normally left for the watch coming on duty at six o'clock.