JPS6141061B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reading method in a device or the like which processes a recording medium by reading an information signal and a clock signal from a recording medium on which the information signal and a clock signal are recorded synchronously.

Conventional magnetic card processing in which an information signal encoded with information and a clock signal for timing are magnetically recorded in synchronization with each other, and the information signal and clock signal are read from the magnetic card and the magnetic card is processed. The device uses the read clock signal to generate gate signals corresponding to each clock signal, gates the read information signal with the gate signal to extract the information signal, and combines the extracted information signal and the clock signal. The magnetic card is configured to be supplied separately to a processing circuit to determine whether the magnetic card is genuine or not, perform arithmetic processing, and the like. However, in such a device, if even one clock signal is missing, the gate signal corresponding to that signal will not be generated.
Therefore, the information signal could not be extracted accurately.

SUMMARY OF THE INVENTION An object of the present invention is to provide an information reading method which can accurately extract an information signal by supplementing the clock signal when the clock signal is missing.

An embodiment of the information reading device shown in the drawings will be described below. FIG. 1 shows an apparatus for reading clock signals and encoded information signals from a magnetic card in which clock signals and encoded information signals are magnetically recorded on separate tracks spaced apart in a direction perpendicular to the card transport direction. An example is shown. In the same figure, 1
a and 1b are magnetic heads for reading, and magnetic head 1
a reads the clock signal and supplies the read clock signal to the shaping circuit 3a via the amplifier 2a; the magnetic head 1b reads the information signal;
The read information signal is supplied to a shaping circuit 3b via an amplifier 2b. The shaping circuit 3a waveform-shapes the input signal to generate a clock signal as shown in FIG. 2A, and supplies this clock signal to the gate signal generator 4 and the auxiliary gate signal generator 5. Further, the shaping circuit 3b shapes the waveform of the input signal, converts it into an information signal as shown in FIG. 2H, and supplies this information signal to the set input of the flip-flop 6.

The gate signal generator 4 is a circuit that generates gate signals corresponding to each input clock signal, and the auxiliary gate signal generator 5 is a circuit that generates gate signals corresponding to the omitted clock signals. Each generator 4, 5 includes two multivibrators 4a, 4b, 5a, 5b connected in series.
The input terminal of a is connected in parallel to the output terminal of the shaping circuit 3a, and the subsequent multivibrator 4
The output terminals of the gates b and 5b are connected to different input terminals of the OR gate 7, respectively.

The multivibrator 4a at the front stage of the gate signal generator 4 is a monostable multivibrator whose time constant _t1 is shorter than the period _T0 of the clock signal, and when the input clock signal rises (or falls).
generates a digital signal that is triggered at a high level for a time _t1 . The time constant t ₁ is approximately 1/2 of the period T ₀ , considering the case where the clock signal and the information signal are not read at the same time and the information signal has a phase shift of 180 degrees with respect to the clock signal. It is preferable to choose. Rear stage multivibrator 4b
is a sampling pulse generator for sampling information, and is composed of, for example, a monostable multivibrator with a time constant of _t2 , and is triggered at the falling edge of the digital signal to generate a gate signal corresponding to the clock signal. In the gate signal generator 4 configured in this manner, if a clock signal is inputted without missing, the multivibrator 4a at the front stage generates a digital signal as shown in FIG. 2B, and the multivibrator 4b at the rear stage generates a digital signal as shown in FIG. generates gate signals corresponding to each clock signal as shown in FIG. 2C. However, if the clock signal is missing, for example, if the clock signal CP in FIG. 2A is missing, the digital signal DP in FIG. 2B is missing from the output signal of the multivibrator 4a. As a result, the gate signal GP in FIG. 2C is omitted from the output signal of the multivibrator 4b. Missing gate signal
GP corresponds to the missing clock signal CP.

The multivibrator 5a at the front stage of the auxiliary gate signal generator 5 is a retrigger type monostable multivibrator having a time constant _t3 that is the sum of the period _T0 of the input clock signal and the time constant _t1 of the multivibrator 4a. Triggered on the rising edge (or falling edge) of the clock signal. The rear multivibrator 5b is made in the same manner as the multivibrator 4b. Therefore, the auxiliary gate signal generator 5
If the clock signal is normal, the output of the multivibrator 5a maintains a high level as shown in FIG.
The output remains at a low level as shown in FIG. 2E. However, if, for example, the _clock signal CP in FIG. is triggered to produce a gate signal as shown by the dotted line in Figure 2E.
Generates GP′. This gate signal GP' has the time constant _t3 of the multivibrator 5a equal to the period of the clock signal.
Since it is selected as the sum of T ₀ and the time constant t ₁ of the multivibrator 4a, it corresponds to the omitted clock signal.

The output signal of OR gate 7 is applied to the inputs C and E in Figure 2.
Therefore, regardless of whether the clock signal is normal or not, the gate signal as shown in FIG. , and the output terminal 10a. The monostable multivibrator 8 is triggered when the input gate signal falls (or rises), generates a reset signal as shown in FIG. 2G, and supplies this reset signal to the reset input terminal of the flip-flop 6. do. The set input terminal of the flip-flop 6 (Q output) is connected to the shaping circuit 3b as described above, so if the information signal is as shown in FIG. 2H, it is as shown in FIG. 2I. Become. This set output is supplied to the second input terminal of AND gate 9. Since the gate signal shown in FIG. 2 F is input to the first input terminal of the AND gate 9, a signal shown in FIG. 2 J is generated at its output.
It is supplied to the output terminal 10b. The signal at the output terminal 10a is supplied as a clock signal to a signal processing circuit (not shown), and the signal at the output terminal 10b is supplied as an information symbol to the signal processing circuit.

In the above device, when the clock signal is deleted midway, the re-trigger type monostable multivibrator 5a terminates its operation when a gate signal corresponding to the deleted clock signal is generated, and thereby the monostable multivibrator 5a terminates its operation. Since the vibrator 5b generates a gate signal corresponding to the omitted clock signal, the information signal can be gated accurately.

Note that the present invention can be applied not only to a method and apparatus for reading magnetic information, but also to a method and apparatus for reading optical information.

As described above, according to the present invention, the re-trigger type timer circuit is triggered by the read clock signal, and if the clock signal is deleted midway, the gate signal corresponding to the deleted clock signal is Since the information signal is generated when the timer circuit ends its operation, the information signal can be accurately gated and extracted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the present invention, and FIG. 2 is a diagram showing waveforms of electrical signals. 1a, 1b...Magnetic head for reading, 4...Gate signal generator, 5...Auxiliary gate signal generator,
5a... Retrigger type monostable multivibrator, 5b... Monostable multivibrator, 6...
Flip-flop, 9...gate circuit.

Claims (1)

[Claims] 1. In an information reading method, a gate signal is generated at the end of the operation of a monostable multivibrator triggered by a read clock signal, and the read information signal is gated with the gate signal and extracted. Trigger a re-trigger timer having a time constant equal to the sum of the period of the clock signal and the time constant of the monostable multivibrator, and when the clock signal is deleted, a gate signal corresponding to the deleted clock signal is triggered. An information reading method characterized in that the information is generated when the operation of the timer ends.