Patent GB-1157860-A (GB)
Title: Improvements in or relating to a Method of and Apparatus for Recording Signals
IPC: H03K3/284
Filed: 1967-06-12
Abstract: 1,157,860. Recording-apparatus. ELECTRO-ACUSTIC G. m.b.H. June 12, 1967 [June 10, 1966], No.27530/67. Heading G1J. [Also in Division H4] The invention relates to a method of measuring and recording wherein the magnitudes assumed by a variable over a very short time interval are stored for a longer measuring time period during which the stored magnitudes are scanned several times and then erased and wherein voltages are obtained one in each scan from a sample only of the stored magnitudes at time intervals which, in successive scans, steadily increase in steps until the end of the measuring period, and wherein the amplitudes of the voltages obtained influence a record made by a pen transversing a record sheet once in each measuring period. As described the invention is applied to supplement or replace a cathode ray tube display in an echo sounding apparatus in which echos received in successive soundings are stored magnetically alternately in tracks SP1 and SP2 on a rotating drum. To each track there is a recording, an erasing and a reproducing head and, during a sounding with a switch U3 in the position shown, echo pulses are continuously stored and then erased from track SP1, while pulses relating to the preceding sounding (made with U3 in the other position), stored in track SP2 and not erased at the moment U3 was switched to the shown position) are repeatedly scanned and reproduced at the rate of rotation of the drum to produce a voltage at a terminal a with corresponding fluctuation of amplitude. A motor M drives a pen N across a record sheet in synchronism with the slide of a potentiometer R in circuit with a multivibrator MM3 whose return delay after actuation is thereby increased linearly. Two further tracks SP'1 and SP'2 with associated heads are arranged to produce square trigger pulses Tr when gaps in the records stored in the tracks SP1, SP2 respectively are scanned, the gaps corresponding to the spaces between recording and erasing heads. When a pulse Tr appears at b, the multivibrator MM3 is actuated and, when MM3 returns, a further multivibrator MM4 changes state for 0À2 ms, causing a rectifier circuit to produce a two-way live connection between terminals f and i, which is broken when the multivibrator MM4 is at rest. Thus at the beginning of each scan a pulse Tr actuates MM3 and the delay in its return (due to the linear increase in resistance from the potentiometer R) increases a step in each scan so that the action of MM4 in connecting the terminals f and i in successive scans produces a stepped voltage variation at i representing the envelope of a succession of samples of the voltage variation reproduced at a throughout the measuring period. The voltage on the terminal i is amplified and applied to the pen N which produces a variable density record in a relatively slow tranverse of the record sheet representing with a sufficient power of resolution the intensity of the echoes received in the very short interval of time taken for the drum to complete the revolution immediately preceding switching between the two tracks.