SU731467A1 - Device for frequency-phase control of magnetic tape motion mean speed - Google Patents

Description

a verter connected between the output of the preamplifier and the second input of the logic circuit and the third matching node connected between the output of the frequency sensor and the third input of the logic circuit, while the fourth input of this circuit is connected to the output of the first matching node.

The drawing shows a functional diagram of the device and the frequency-phase device for controlling the average speed of the magnetic tape.

The device contains a magnetic reproduction head 1, conjugated with magnetic tape 2 and connected to the imitational amplifier 3 of the control signal, and the series-connected source 4 of the signal frequency of the two outputs, the phase-sensitive element 7 with the two inputs S and 9, the integrating unit 10 s two inputs // and 12, to the second input 12 of which is connected - a frequency sensitive element 13, a controlled power source 14 and an electric motor 15, are directly connected to the frequency tachometer 1-6 and black Ez. master node 17 coupled with magnetic tape 2.

The device also contains serially connected and connected to the output of the preamplifier 3, rectifier 18, integrator-limiter 19, threshold shaping unit 20, limiter 21 of the lower signal level, first matching node 22, first inverter 23, logic circuit 2X2I - OR - NOT 24 s four inputs 25-28 and a controlled frequency divider 29 with inputs 30 and 31, the output of which is directly connected to the input of the frequency-sensitive element 13 and through the extender 33 of the capture band with two inputs 33 and 34, the second input 34 is connected source to the second output 6 of the source 4 signal of the reference frequency. It is connected to the second input 9 of the phase-sensitive element 7.

In addition, the device contains a serially connected second matching node 35 and a second inverter connected between the same output of the preamplifier J and the second input 26 of the 2X2I circuit - OR - NOT 24, and the third matching node 37, connected between the output of the frequency control and the third input 27 2X2I circuits - OR - NOT 24. At that, the fourth input 28 of the 2x2I circuit - OR - NO 24 is connected to the output of the first matching node 22, and the second input 31 of the controlled frequency divider 29 is connected to the speed switching bus 38.

The device works as follows.

Reproduced from the magnetic tape 2 by the entertainment head / the control frequency signal is fed to the preamplifier 5 of the control signal, from the output of which the generated pulses are fed to the matching node 35 to match the output of the pre-amplifier to the input of the second inverter 55. From the output of the inverter 36, the control signal goes to the second input 25 2x2I- OR - NOT 24 circuits. At the same time, the control signal from the same output of the preamplifier 3 control signal is fed to the rectifier 18, where the signal is p ml is also in the form of a constant voltage (supplied to integrator-011, the corrector 19. Here, the rectified signal is integrated and limited from above in amplitude, and in the form of a constant voltage goes further to the threshold forming node 20.

When a signal arrives at the input, a high voltage level is applied to the limiter 21 of the lower signal level, which is necessary to ensure the noise immunity of the considered part of the device when the control signal coming from the magnetic tape disappears. The signal from the limiter 21 through the first matching node 22, which forms the logical zero level at the output, goes to the fourth input 28 of the 2X2I circuit - OR - NOT, 24 and prohibits the passage of signals from the frequency tachometer 16 coming through the matching device 37 to the third input of the 2X2I circuit. OR NOT 24.

At that time, the logical zero level from the output of the first matching node 22 is fed to the input of the first inverter 23, which forms a signal with the level of the logical unit that is fed to the first input of the 2X2 AND -OR-HE 24 circuit and allows the passage of control signals from the output of the second inverter 36 to the second input 26 of the circuit 2HYI - OR - NOT 24.

If a pilot signal produced from a magnetic tape / falls out, for example, as a result of a lazy amplitude module, the signal at the output of the preamplifier 3 of the control signal disappears, and therefore the voltage at the output of the rectifier 18 and the limiter integrator 19 is absent . As a consequence, at the output of the threshold forming node 20, a low voltage level appears, which enters the input of the lower limiter 21, which forms a signal with a zero voltage level, coming through the first matching node 22, which in this case generates a signal with a level of logical one , to the fourth input 28 of the 2X2I circuit - OR-NOT 24, as a result of which a passage to the output of the 2X2I circuit - OR - NOT 24 signals of the frequency sensor 16, arriving at its third input 27 is allowed. At the same time, at the output of the first inverter 23 urov1nem signal from a logic zero input to the first input of OR gate 25 2H2I- - NO 2 (4 .i prohibiting passage of the interference signal occurring in the head reproducing / control a roll of tape I1gnala 2.5

As a result of the described logical processing of the generated control frequency signals. The frequency tachometer 16 signal appears during the reproduction of the control signal, instead of filling with a signal from the frequency tachometer 16, thereby ensuring the continuous presence of the control signal at the output of the 2X2I circuit - OR - NOT 24. The control signal from the output of the circuit 15 2Х12И - OR - NOT 24 goes further to the first IQ 30 controlled frequency divider 29, to the second input / which through the bus 38 of the speed switch, is fed NDA 20 for energizing respective coefficient.

From the output of the controlled frequency divider 29, the signal of the control frequency is fed to the input of the frequency sensitive element 13, which forms 25 square pulses, the frequency and the magnitude of which are directly proportional to the frequency of the control signal, i.e. the speed of movement of the magnetic tape. Next, the signal from the output of the frequency-sensitive element 13 is fed to the second input of the integrating summing node 10, which generates control voltage from the rectangular pulses to the controlled power source 14, which produces the power supply voltage for the DC electric motor 15 , through the master node 17 interfaced with magnetic tape 2. The control voltage produced by the frequency-frequency | Italion element 13 and the integrating-summing node 10 is proportional to the frequency and duty cycle of the control of the signal reproduced from the magnetic. NIT1NOY tape 2, is changed so as to maintain the nominal speed of movement of the magnetic tape with an accuracy of a few percent to 45, which is necessary to ensure the normal operation of the phase-sensitive element 7 within the zone of the capture band.

As a result of the interaction of the signals of the reference and reference frequencies at the inputs 5 and S of the phase-sensitive element 7, a constant overvoltage develops at the output, pronoschialno phase difference 55 equal signals, which enters the first input // integrating-summing node 10, which is summed by with the voltage produced by the frequency-sensitive element, /, which 60

The speed of movement of the magnetic tape with the accuracy provided by the source of the reference frequency 4.

Thus, the proposed device makes it possible to completely eliminate failures of the phase-sensitive and frequency-sensitive elements when the pilot signal falls out, which makes it possible to increase the accuracy of adjusting the average speed of the magnetic tape.

Claims (2)

1. Copyright certificate - USSR .№ 493801, cl. G 11 B 15/46, 1974. 2. US patent No. 3356921, cl. SISSIS, publ. at. 1967 (prototype).