Echo sounder with coded acoustic depth signal - has echo return interval coded and compared with stored values

摘要

The echo sounder provides an acoustic depth signal for navigation of ships within shallow waters etc. The interval between an emitted pulse and the received corresponding echo, comprising an indirect indication of the depth is measured and this measured interval is electronically coded before comparison with predetermined stored values. The comparator output signal is transposed electro-acoustically to provide an acoustic depth signal. The coding device comprises a selective coupling circuit receiving the emitted and received pulses, its output supplied to a bistable stage coupled to an oscillator and a counter. The oscillator is enabled by an emitted pulse and blocked by a received echo pulse, with the counter recording the oscillator pulses between them.