SU767827A1 - Device for playing-back data from magnetic tape - Google Patents

Description

(54) DEVICE FOR PLAYING INFORMATION WITH MAGNETIC TAPE

one

The invention relates to computing and can be used in storage devices on a magnetic tape to reproduce recorded information from it.

A device for reproducing digital information from a magnetic carrier of signals is known, comprising a circuit of a series-connected magnetic head, an amplifier, a detector and a former connected simultaneously to three electrical circuits parallel to each other, the first of which consists of an AND circuit, and the second is of a serially connected circuit. delays and a gating unit, and a third from another AND circuit, a gating unit, a prohibition circuit, and a driver, and the device is equipped with two additional delay circuits ki, each of which is connected between its AND circuit and the gating unit 1.

This device is complex, contains many elements and blocks, and with the technical implementation requires significant hardware costs.

A device for selecting signals is known, which contains an information and synchronization signal extraction unit, whose information input is connected to the device input, and a control input to the first output of the control unit, a display unit indicating the termination of synchronization signals, the input and output signal are connected respectively to the output of the control unit and output of the device, and a block of analysis of the read code, connected by its input to the selection block of information and syncpb down to d d signal, and its output to the input of the control block neither 2.

ten

This device also requires significant hardware costs. An information and synchronization signal allocation unit serves to distribute over two

15 buses of the sequence of information and synchronizing signals from a serial binary code read from a magnetic disk drive written in a manner without returning to Zero.

20 At the start of operation, the special counting trigger in this block is set to the zero position by the reset signal. In the process of work in case of a failure, the device works incorrectly until

Ex until the installation signal to the initial position is given again:

It is also known a device for reading a signal from a magnetic carrier, which holds a zero level detector connected to the information input of the device, a rigger, one of the coordinate inputs of the coordinator is connected to the control input of the device, and delay elements, AND, OR elements, and the output of the Level Detector is connected Orbits directly or through the first delay element and connected to the first inputs of the AND elements, the second inputs of which are connected to the outputs of the trigger connected by their counting input through a second delay element to the output element 3 OR.

This device distributes on two buses the pulses of the self-synchronizing code read from the magnetic carrier, which is a sequence of synchronizing pulses following with an interval T between which there are information pulses (when writing one). The common pulse sequence has a double frequency. When recording zero information pulses are missing, and the frequency is equal to the frequency of the clock pulses. At the same time, any array readable from the storage medium must always begin and end with a synchronous pulse — this is a drawback of the device. At the beginning of the operation, by applying a signal to the control input, the trigger is set to the initial (single) state, thus the device is prepared for operation — the need for pre-tuning is a disadvantage of the device. In the case of a crash, the device does not work correctly until the next setting - this is also its bad flaw.

The closest known from the technical essence is the device for reproducing a binary code, recorded by a return to zero method, containing a read head and a signal separation unit. With this device, a positive pulse, followed by a negative one, is decoded as a binary one, and the opposite combination of pulses is interpreted as a binary zero 4.

The disadvantage of the device is that its operation requires synchronizing pulses, which must be obtained from an additional source.

The purpose of the invention is to increase reliability by providing self-synchronization of the device. : - The goal is achieved by the fact that four AND elements, two delay elements and a trigger, whose inputs are connected respectively, are inserted into a device for data logging from a magnetic tape containing a magnetic read head connected to the input of a pulse shaper.

with the outputs of the first and second elements And, the outputs of the trigger are connected to one of the inputs of the third and fourth elements And, the other inputs of which are connected to the outputs of the pulse shaper and with one of the inputs of the first and second elements And, the other inputs of the first and second elements And connected through elements delays with pulse driver outputs.

The drawing shows the functional diagram of the proposed device.

0 The device contains a magnetic head 1 for reading, a shaper 2 pulses, elements 3 and 4 delays, elements 5-8 I, trigger 9.

The device works as follows. Magnet1 / & The head 1 converts the information recorded on the carrier into electrical signals, which are fed to the input of the driver 2 pulses.

Positive signals are routed to one output of a signal separation unit.

0 negative - to another. On . At the outputs of the pulse former 2, pulses of sufficient duration are formed so that they can coincide after the delay element, but less than half of the clock period (the optimal duration is T / 4).

5 The delay of elements 3 and 4 is equal to half of the clock period, therefore, if the pulses follow one after another through half of the clock period (this happens during the transition from binary to binary

zero and vice versa), they coincide on the elements of And 5 and 6, the outputs of which appear pulses, which throw the trigger 9 on the corresponding to the setup input. At the output of the element 7 And pass pulses corresponding to

S the binary units of the information read, to the input of the element 8 And the pulses corresponding to the binary zero are passed.

The proposed device is easily implemented, has simplicity and reliability and provides self-synchronization when

read the code.

Claims (4)

Invention Formula A device for reproducing information from a magnetic tape, containing a magnetic read head connected to the input of a pulse shaper, characterized in that, in order to increase reliability by providing self-synchronization of the device, four And elements are introduced into it, two delay elements and a trigger, whose inputs are among respectively, with the outputs of the first and second elements And, the outputs of the trigger are connected to one from the inputs of the third and fourth elements And, the other inputs of which are connected to the outputs of the pulse shaper and with one of the inputs of the first and second elements And, the other inputs of the first and second elements And connected via delay elements to the pulse driver outputs. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 447746, cl. G 11 B 5/02, 1974. 2. USSR author's certificate number 469132, cl. G II 5/02, 197.3. 3. USSR author's certificate number 506046, cl. G 11 B 5/02, 1974. 4.Flores A. External computer devices. M., “Peace, 1977, p. 270 (prototype).