ECHO SOUNDER

摘要

1,244,698. Echo sounders; pulse circuits. FRIED. KRUPP G.m.b.H. 1 Aug., 1969 [3 Aug., 1968], No. 38636/69. Addition to 1,204,939. Headings H3T and H4D. In a development of the echo-sounder in the parent Specification (Division H4) an additional echo-duration selector 24 is provided in which the output pulse of the duration-sensitive Schmitt trigger 9 is compared with a locallygenerated reference pulse of predetermined maximum duration. Monostable 28 is triggered by the Schmitt 9 output c to give the reference pulse v, and logic circuits 27 give an output signal k only if c is of greater duration than v. Only if signal k is present will gate 25 supply a stop signal to the depth-indicating counter 7. Alternatively, duration-selector 24 may be arranged to give a signal k only if c is of shorter duration than v. A further duration-selector (24a) and counter (71) may be added (Fig. 4, not shown) for indicating those echoes whose duration lies between two selected limits. Circuit details.-The duration of the unstable state of monostable 28 (i.e. the duration of reference pulse v) is made equal to the duration of the triggering pulse c, so long as pulse c does not exceed the predetermined maximum duration of pulse v (which is fixed by the time constant of R and C) by providing diode 29 across the monostable. This ensures that a brief interference pulse triggering the monostable will not prevent a longer useful input pulse from triggering the monostable shortly afterwards.