Abstract
Measurements of performance and system delay were carried out on two sets of frequency shift keying (F.S.K.) equipment. The application of this type of equipment for transmitting variable time-spaced pulses from vehicle detectors located at remote sites are discussed. A technique for correcting de-graded contact pulses from pneumatic axle detectors is also described. The investigation showed that it was possible to maintain a sufficiently accurate separation of pairs of pulses following their transmission over G.P.O. lines using either of these two sets of F.S.K. equipment.