RU1540558C - Device for controlling reversal of magnetic tape - Google Patents

Abstract

FIELD: magnetic recording. SUBSTANCE: device comprises three input buses 1, 2 and 4 of control signals and input bus 3 of playback signal, reference frequency generator 6, pulse shaper 9, four AND circuits 5, 13, 14 and 17, three inverters 7, 10 and 11, three counters 8, 12 and 15, flip-flop 16 and three decoders 18, 19 and 20 with connections. Decoder outputs serve as outputs of the device proper. AND circuit 5 and counter 8 with connections make it possible to detect in advance the beginning of flow of information recorded on magnetic tape either continuously or in the form of information blocks with pauses therebetween. EFFECT: higher reliability of stopping or reversing magnetic tape. 2 cl, 1 dwg

Description

 The invention relates to techniques for magnetic recording.

 The purpose of the invention is to increase the reliability of stopping or reversing a magnetic tape in the same zone when changing speeds.

 The drawing shows a functional diagram of the proposed device.

It contains the input bus 1 of the control signal "Start", the input bus 2 of the control signal f ₈ , the input bus 3 of the playback signal, the input bus 4 of the control signal "Direction", a coincidence circuit 5, a reference frequency generator 6, an inverter 7, a counter 8, a shaper 9 pulses, inverters 10 and 11, reference frequency counter 12, coincidence circuits 13 and 14, counter 15, trigger 16, coincidence circuit 17, track end decoder 18, tape start decoder 19, tape end decoder 20 and output buses 21-23.

 Coincidence patterns 5, 13, 14 and 17 are elements of type 2I-NOT.

 The input bus 1 of the control signal is connected to the first input of the fourth matching circuit 14 and in addition to the installation input of the trigger 16. The input bus 3 of the playback signal is connected to the input of the pulse shaper 9, made in the form of a comparator. The input bus 4 of the control signal is connected to one of the inputs of the decoder 20 of the end of the tape and to the input of the second inverter 7, the output of which is connected to one of the inputs of the decoder 19 of the beginning of the tape. The output of the pulse shaper 9 is connected to the input of the third inverter 10, with the installation input of the first counter 8 and the first input of the second coincidence circuit 13. The output of the reference frequency generator 6 is connected to the counting input of the reference frequency counter 12 and to the first input of the first coincidence circuit 5, the output of which is connected to the counting input of the first counter 8. The output of the counter 8 is connected to the second input of the first coincidence circuit 5 and to the installation input of the second counter 15 the output of which is connected to the counting input of the trigger 16 and to the input of the first inverter 11, the output of which is connected to the second input of the third coincidence circuit 17 and to the second input of the second coincidence circuit 13, the output of which is connected to the counting input of the WTO horn counter 15. The output of the fourth match circuit 14 is connected to the installation input to the trigger unit 16, the output of which is connected to the second input of the fourth match circuit 14 and to the first input of the third match circuit 17, the output of which is connected to the second installation input of the reference frequency counter 12, the first the installation input of which is connected to the output of the third inverter 10. The outputs of the counter 12 are connected to the inputs of the decoders 18-20, the outputs of which are connected to the output buses 23-21, respectively.

 The proposed device operates as follows.

 An information signal in the form of a continuous sequence of pulses or in the form of information blocks with pauses of a given length between them is preliminarily recorded along the entire length of the working section of the tape, at the ends of which there is no information wound on the receiving and feeding coils.

 If there is no movement of the magnetic tape in the tape drive mechanism, the device is in its initial state, while the signal level on the input bus 1 "Start" blocks the operation of the coincidence circuit 14 and trigger 16, at the direct output of which the logic level is set to "0", which goes to the inputs of the circuits 14 and 17 of the match, coding the logic level “1” at their outputs, this level from the output of the match circuit 14 goes to the installation water in the “1” of the trigger 16, from the output of the match circuit 17 to the second installation input of the counter 12, to the first installation the input of which also receives the logical level “1” from the output of the inverter 10, at the input of which the logical level “0”, coming from the output of the pulse shaper 9, the logical levels “1” at the installation inputs of the counter 12 block its operation and set the levels at its outputs logical "0", which ensures the absence of signals at the outputs of decoders 18-20, the level of logical "0" from the output of the pulse shaper 9 additionally goes to the first input of the coincidence circuit 13, blocking its operation, and to the installation input of the counter 8, the fulfillment of which the reference frequency signal coming from the output of the reference frequency generator 6 through the coincidence circuit 5, the logical level "1" is encoded at the output, which goes to the second input of the coincidence circuit 5, blocking the passage of the reference frequency signal through it, additionally the signal from the output of the counter 8 fed to the installation input of the counter 15, which provides at its outputs a level of logical "0".

 Before starting the movement of the magnetic tape to the input bus 4 of the control signal, a signal of the selected direction is applied in the form of a constant level of logic "1" or logical "0", which is fed to one of the inputs of the decoder 20 and through the inverter to one of the inputs of the decoder 19, while on the input bus 4, the logical level “1” corresponds to the direction “Forward”, the level of the logical “0” corresponds to the direction “Reverse”. The signal "Start" on the input bus 1 of the control signal sets the logical level "1" and the movement of the magnetic tape begins, the same voltage level removes the lock from the installation input to "0", trigger 16 and the first input of the match circuit 14. The device saves this state until an amplified playback signal appears on the input bus 3, and as a result, the first pulse is output at the output of the driver 9, the voltage level change at the output of which leads to a short-term start of the counter 12 and to the reset of the outputs of the counter 8 to zero, which allows operation counter 15.

 Upon further receipt of the reproduced signal on the input bus 3 by each pulse from the output of the pulse shaper 9, the counter 12 is briefly started, the counter 8 is reset, the counter 15 matches through the circuit 13, and when it is filled, the signal from its output through the inverter 11 interrupts further passage through the circuit 13 matches information pulses coming from the output of the shaper 9, at the same time the signal from the output of the counter 15 causes the trigger 16 and its blocking through the coincidence circuit 14, which Starting detection start the flow of information. In addition, the signal from the output of the trigger 16 is fed to the first input of the coincidence circuit 17, the logical “0” level is supplied to the second input of the inverter 11, which stores the logical “1” level at the output of the coincidence circuit 17 and provides a periodic reset of the counter contents by 12 pulses with shaper output 9.

2^n-1 выход счет- чика 8 принимает состояние логической "1", что приводит к сбросу счетчика 15 и подаче через инвертор 11 на второй вход схемы 17 совпадений уровня логической "1", с выхода которой уровень логического "0" поступает на второй установочный вход счетчика 12, который начинает заполняться импульсами опорной частоты, с этого момента счетчик 12 не может быть сброшен помеховыми сигналами, поступающими на его первый установочный вход через инвертор 10, с выхода формирователя 9 в виде одиночных импульсов или группы импульсов, так как для сброса содержимого счетчика 12 необходимо заполнить счетчик 15, что требует поступления на его вход непрерывной последовательности импульсов, численно равной 2^k-1 с частотой следования, большей f_оп/2^n-1 (n - разрядность счетчика 8), невыполнение второго условия приводит к периодическому заполнению - сбросу счетчика 15 без изменения уровня сигнала на его выходе, что исключает сброс содержимого счетчика 12. В результате заполнения счетчика 12 импульсами опорной частоты на выходе дешифратора 18 формируется сигнал предупреждения окончания дорожки, затем через выбранный временной интервал на выходе одного из дешифраторов 19 или 20 в зависимости от выбранного направления формируется один из сигналов конца или начала ленты, по которому движение магнитной ленты переходит в режим торможения, а на входную шину 1 управляющего сигнала поступает уровень логического "0", которым устройство возвращается в исходное состояние.At the end of the control or information signal flow, the logical level “0” is established at the output of the shaper, by which the counter 12 is blocked through the inverter 10, after a time interval t _o ≈

2 ^{n-1 the} output of counter 8 takes a logical “1” state, which leads to a reset of counter 15 and a logical “1” level is supplied to the second input of the coincidence circuit 17 through the inverter 11, from the output of which the logical “0” level goes to the second the installation input of the counter 12, which begins to be filled with pulses of the reference frequency, from this moment the counter 12 cannot be reset by interference signals supplied to its first installation input through the inverter 10, from the output of the shaper 9 in the form of single pulses or a group of pulses, since for reset with erzhimogo counter 12 must fill meter 15, which requires entry into its continuous sequence of pulses input numerically equal to 2 ^k-1 with a repetition frequency greater than f _op / 2 ^n-1 (n - bit counter 8), the failure of the second condition causes a periodic filling - resetting the counter 15 without changing the signal level at its output, which eliminates the reset of the contents of the counter 12. As a result of filling the counter 12 with the pulses of the reference frequency at the output of the decoder 18, a track end warning signal is generated, then the selected time interval at the output of one of the decoders 19 or 20, depending on the selected direction, one of the signals of the end or beginning of the tape is formed, along which the magnetic tape moves into braking mode, and the logic level “0” is received at the input bus 1 of the control signal, which the device returns to its original state.

 After the magnetic tape is completely stopped, the voltage level opposite to the previously selected direction is applied to the input bus 4 of the control signal, then the logical level “1” is applied to the input bus 1 “Start”, and the magnetic tape starts moving in the opposite direction along the section of the magnetic tape defined above conditions and relationships, starting from the moment the flow of information ends.

To ensure reliable operation of the device, the time intervals worked out by the counters 8, 12 and 15 must satisfy the condition t ₁₂ > t ₁₅ > t ₈ , which is ensured by the appropriate choice of the bit depth of the counters, while the filling of the first counter 8 with the signals of the reference frequency generator 6 should occur at least than four periods of the lowest frequency information signal.

 To ensure the operation of the device from information recorded on magnetic tape in the form of blocks with inter-block pauses, the time interval processed by the counter 12 for the signal "End of track" should be longer than the duration of the inter-block pause, and the information capacity of the block should be greater than the information capacity of the counter 15, for example , twice or more.

In this case, the information flow is detected during the reproduction of the first information block, at the end of each information block, at the time interval t ₈ = 2 ^n-1 / f _op at the output of counter 8, the logical level “1” is established, which resets the contents of counter 15, setting to its output, the logic level is “0”, which causes the counter 12 to start for a time equal to the duration of the inter-block pause, plus the time it takes to fill the counter with 15 pulses of the next information block coming from the output of the former 9, after resets the contents of the 12 counter start - discharge which from this moment until the end of the information unit is derived from the output pulse shaper 9. After the last information block operation of the apparatus is similar to the information flow neprepyvnym. The same conditions and ratios determine the noise immunity of the device when reproducing a continuous stream of information.

 To ensure a stop or automatic reverse of the magnetic tape in the same zone when changing speeds in the device circuit, the counting input of the counter 12 is supplied with pulses from the input bus 2, while the counter 12 is filled with pulses, the repetition rate of which is proportional to the angular frequency of rotation of the electric motor, angle the rotation of which determines the distance traveled by the magnetic tape in the path of the tape drive mechanism and, therefore, the operation of the counter 12 occurs at the same distance from the ends of the masses va information recorded on a magnetic tape, regardless of the speed.

Claims (1)

 1. DEVICE FOR MANAGING THE REVERSE OF A MAGNETIC TAPE, comprising a reference frequency generator, a reference frequency counter, a counting input of which is connected to the output of the generator, a pulse shaper, three decoders, the outputs of which are the output buses of the device, the input bus of the reproduction signal connected to the input of the pulse shaper, and three input buses of control signals, characterized in that, in order to increase the reliability of controlling the reverse of the magnetic tape by reducing false positives, two counters are introduced into it a trigger, four coincidence circuits and three inverters, while the first input of the first coincidence circuit is connected to the output of the reference frequency generator, and the output is connected to the counting input of the first counter, the installation input of which is connected to the output of the pulse shaper and to the first input of the second coincidence circuit, and the output of the first counter - with the second input of the first matching circuit and with the installation input of the second counter, the output of which is connected to the input of the first inverter and to the counting input of the trigger, the output of the first inverter is connected to the second input the third coincidence circuit and to the second input, the second is the output of the twelfth element NOT, the input of which is connected to the first inputs of the seventeenth and eighteenth elements AND, the second inputs of the fifteenth and sixteenth elements AND and the input of the eleventh category of the information input of the sign analysis unit, the input of the twelfth category of the information input of which is connected to the first inputs from the twenty-third to the twenty-sixth elements AND and the input of the thirteenth element is NOT, the output of which is connected to the first inputs of the twenty-first, twenty the second, twenty-seventh and twenty-eighth elements And, the input of the tenth category of the information input of the sign analysis unit through the fourteenth element is NOT connected to the second inputs from the twenty-first to twenty-fourth elements And, the third input of the twenty-first element And is connected to the second input of the twenty-eighth element And, the input of the tenth element is NOT and the output of the third node of the formation of the sign, the output of the tenth element is NOT connected to the third and second inputs, respectively, of the twenty second and twenty-eighth elements AND, output n the first sign-forming unit is connected to the third and second inputs of the thirteenth and nineteenth AND elements, respectively, and the input of the eighth element of NOT, the output of which is connected to the third and second inputs of the fourteenth and twentieth elements AND, the output of the second sign-forming unit is connected to the third and second inputs, respectively, of the fifteenth and the seventeenth elements AND and the input of the ninth element is NOT, the output of which is connected to the third and second inputs, respectively, of the sixteenth and eighteenth elements OR , the output of the fourth node of the formation of the sign is connected to the third and second inputs of the twenty third and twenty fifth elements AND, respectively, and the input of the eleventh element NOT, the output of which is connected to the third and second inputs of the twenty fourth and twenty sixth elements And, outputs from the thirteenth and twenty eighth And elements are connected to the outputs, respectively, from the first to the sixteenth block of the sign analysis.