JP4266991B2 - Magnetic card reader - Google Patents

Description

  The present invention relates to a magnetic card reader, and more particularly to an improvement in reading performance of a magnetic card reader for a demagnetizing card.

  An example of a conventional magnetic card reader is shown in FIG. The magnetic card reader 60 of FIG. 6 is for reading F2F format magnetic recording information recorded on a magnetic card (not shown), and includes a magnetic head 61, an amplification unit 62, an F2F demodulation unit 63, and a decoding unit 64. have.

  In this magnetic card reader 60, the magnetic head 61 reads the magnetic recording information recorded on the magnetic card and outputs an analog signal corresponding to the read magnetic recording information. The amplifying unit 62 amplifies the analog signal from the magnetic head 61 and outputs it to the F2F demodulating unit 63. The F2F demodulator 63 demodulates the analog signal amplified by the amplifier 62 and outputs a clock signal and a data signal. The decoding unit 64 receives the clock signal and the data signal from the F2F demodulation unit 63 and decodes the data signal.

  In addition, another conventional magnetic card reader is configured to automatically perform reset when a card reader control circuit that performs editing processing such as code conversion is stalled due to the influence of noise or the like (for example, , See Patent Document 1).

  Further, another conventional magnetic card reader is configured to report a level abnormality when the read magnetic signal is very small (see, for example, Patent Document 2).

JP-A 64-38821 Japanese Utility Model Publication No. 6-52003

  When a normal magnetic card is read using a conventional magnetic card reader, the analog signal output from the magnetic head has a waveform as shown in FIG. 7, for example.

  On the other hand, when the magnetic recording information recorded on the magnetic card is partially demagnetized for some reason, the analog signal output from the magnetic head has a waveform as shown in FIG.

  In order to correctly demodulate an analog signal having a waveform as shown in FIG. 8, it is necessary to increase the reading sensitivity of the magnetic card reader (or increase the amplification factor of the amplification unit). However, when the reading sensitivity of the magnetic card reader is increased, there is a high possibility that noise is erroneously recognized as a signal (data).

  FIG. 9 is an enlarged view of the head portion of the analog signal waveform of FIG. As shown in FIG. 9, when noise is present at the beginning of the analog signal waveform, if the reading sensitivity of the magnetic card reader is increased, this noise is also recognized as a signal, which adversely affects subsequent data decoding. It will be.

  Hereinafter, the operation of the F2F demodulator 63 of the conventional magnetic card reader shown in FIG. 6 will be described separately for the case where noise is present before the analog signal and the case where noise is not present.

  When there is no noise before the analog signal, an analog signal as shown in FIG. 10A is input to the F2F demodulator 63. That is, several tens of preamble bits are input. The preamble bits all represent logic 0, and in the F2F format, the bit width is wider than the bits representing logic 1.

  The F2F demodulator 63 discards (synchronizes) a predetermined bit (here, 4 bits) at the beginning of the input analog signal, and thereafter, as shown in FIGS. 10B and 10C, the card running signal Is changed to a low level and a clock signal is output. The card running signal is a signal for informing the decoding unit 64 that the card is being read.

  Further, the F2F demodulator 63 determines whether each bit is logical 0 or 1 by comparing the bit width of each bit of the input analog signal with the bit width of the previous bit. The F2F demodulator 63 outputs a high level as a data signal when the input analog signal is logic 0, and outputs a low level when it is logic 1. In the range shown in FIG. 10A, all bits of the analog signal all represent logic 0. Therefore, the F2F demodulator 63 continues to output a high level representing logic 0 as a data signal even after the discarding operation. . Thereafter, when a logic 1 indicating the head of data is input, the F2F demodulator 63 outputs a low level as a data signal for the first time.

On the other hand, when there is noise at the head of the analog signal, the analog signal as shown in FIG. 11A is input to the F2F demodulator 63. In this case, the F2F demodulator 63 determines that the noise is the head of the preamble and performs a discarding operation. For this reason, the F2F demodulator 63 finishes the discarding operation at an earlier stage than in the normal case, and changes the card running signal to a low level as shown in FIGS. Output. Although the pulse width of the clock signal is determined by the bit width of the analog signal that has been discarded, it is recognized here that the leading bit width is wider than the bit width of the preamble due to the influence of noise. Become.

The F2F demodulator 63 also determines whether each bit is logic 0 or 1 by comparing the bit width of each bit of the input analog signal with the bit width of the previous bit. At this time, as described above, when it is recognized that the leading bit width is wider than the preamble bit width due to the influence of noise, the subsequent preamble bits have a bit width smaller than that, that is, are determined to be logic 1. Therefore, as shown in FIG. 11D, a low level is output as a data signal.

  As described above, the conventional magnetic card reader has a problem in that when reading sensitivity is improved to cope with a demagnetization card, noise is detected, and as a result, correct demodulation cannot be performed.

  Accordingly, an object of the present invention is to provide a magnetic card reader capable of demodulating an analog signal read without being affected by noise even when the reading sensitivity of the magnetic card reader is increased.

  Note that Patent Documents 1 and 2 described above do not disclose or suggest the influence of noise when the reading sensitivity is increased or when the reading sensitivity is increased, and do not provide any suggestion about the present invention.

A first aspect of the present invention is a magnetic card reader including a demodulator that demodulates an analog signal obtained by reading magnetic recording information recorded in the F2F format with a magnetic head, wherein the demodulator is a head of the analog signal. Provided with a reset circuit that resets the demodulator when the synchronization is performed using a predetermined number of bits , and then performs the synchronization again on the analog signal input to the demodulator. .

According to a second aspect of the present invention, in the magnetic card reader provided with a demodulator for demodulating an analog signal obtained by reading magnetic recording information recorded in the F2F format with a magnetic head, the demodulator is a head of the analog signal. After the predetermined number of bits are synchronized, the demodulator is reset when it is determined that there is noise until the predetermined time elapses , and then the analog signal input to the demodulator is synchronized again. A reset circuit is provided to be performed .

According to a third aspect of the present invention, in a method for reading a magnetic card having magnetic recording information in F2F format, the magnetic recording information is converted into an analog signal, and a demodulator uses a predetermined number of bits from the beginning of the analog signal. When the synchronization process is performed , the demodulator is reset, and then the synchronization process is started again for the analog signal input to the demodulator .

According to a fourth aspect of the present invention, in a method for reading a magnetic card having magnetic recording information in F2F format, the magnetic recording information is converted into an analog signal, and a demodulator uses a predetermined number of bits from the beginning of the analog signal. If it is determined that there is noise within a predetermined time after the synchronization processing , the demodulator is reset, and then the synchronization processing is started again for the analog signal input to the demodulator. Features.

  According to the present invention, the demodulator is reset after a predetermined discarding operation, and the reading operation is performed again, so that even if there is noise at the head of the magnetic information, the read analog signal is correctly demodulated. can do. As a result, even when the reading sensitivity of the magnetic card reader is increased, demodulation can be performed correctly without being affected by noise.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of a magnetic card reader 10 according to the first embodiment of the present invention. As shown in the figure, the magnetic card reader 10 according to the present embodiment includes a magnetic head 11, an amplification unit 12, an F2F demodulation unit 13, a decoding unit 14, and a reset circuit 15. Here, the magnetic head 11, the amplifying unit 12, and the decoding unit 14 are the same as the conventional ones. The F2F demodulator 13 is the same as the conventional one except that it is reset by the reset circuit 15.

  As will be described later, the reset circuit 15 is for resetting the F2F demodulator 13 based on the output signal from the F2F demodulator 13.

  Hereinafter, the operation of the magnetic card reader 10 according to the present embodiment will be described with reference to FIG.

  The magnetic head 11 reads magnetic recording information recorded on a magnetic card (not shown) and outputs an analog signal. Magnetic recording information is recorded on the magnetic card in the F2F format, and the analog signal is a signal in which the bit width representing the logic 0 is larger than the bit width representing the logic 1.

  The amplifying unit 12 amplifies the analog signal from the magnetic head 11 and supplies it to the F2F demodulating unit 13.

  When the input analog signal is as shown in FIG. 2A, the F2F demodulator 13 discards a predetermined number of bits from the head of the input analog signal (synchronization processing), and FIG. As shown in b), the card running signal is changed to active (low level).

  At this time, the reset circuit 15 detects that the card running signal output from the F2F demodulator 13 has changed to an active state, and outputs a reset signal to the F2F demodulator 13. Thereafter, the reset circuit 15 stops its operation for a predetermined time (a time longer than the time required for the F2F demodulation unit 13 to discard the read).

The F2F demodulator 13 is disabled in response to the reset signal from the reset circuit 15, returns the card running signal to the high level, and also returns the data signal to the high level, so that a predetermined number of bits are again applied to the analog signal. Discard it. Then, F2F demodulator 13, after discarding operation, changing the card traveling signal active (low level) again, and outputs a clock signal as shown in Figure 2 (c).

As described above, in the magnetic card reader of FIG. 1, once a predetermined bit is discarded in the F2F demodulator 13, the reset circuit 15 resets the F2F demodulator 13. As a result, the F2F demodulation unit 13 can correctly demodulate the analog signal without being affected by noise before the head of the analog signal preamble. Thus, the data signal output from the F2F demodulator 13 is maintained at a high level representing the preamble bit (logic 0) until the end of the preamble, as shown in FIG. 2 (d).

  The decoding unit 14 decodes the data signal output from the F2F demodulation unit 13 by using the clock signal output from the F2F demodulation unit 13.

  In the magnetic card reader according to the present embodiment, the F2F demodulating unit 13 once performs a discarding operation for a predetermined number of bits even when an analog signal having no noise is input before the head of the preamble. It is reset and a second read-out operation is performed again.

  Next, the specific configuration and operation of the reset circuit 15 used in the magnetic card reader of FIG. 1 will be described with reference to FIGS.

  As shown in FIG. 3, the reset circuit 15 includes a first monostable multivibrator 31 that generates a preliminary reset signal having a first pulse width t1 when the card running signal changes to active, and a first monostable multistable A second monostable multivibrator 32 that generates a reset mask signal having a second pulse width t2 in response to a preliminary reset signal from the vibrator 31, and a first RC time constant circuit 33 that defines a first amplitude t1. And the second RC time constant circuit 34 defining the second amplitude t2, the preliminary reset signal from the first monostable multivibrator 31, and the reset mask signal from the second monostable multivibrator 32 A NAND circuit 35 that outputs the product as a reset signal to be supplied to the F2F demodulator 13. FIG. 3 shows an example in which the first and second monostable multivibrators 31 and 32 are realized by using one dual retriggerable monostable multivibrator (74HC123). FIG. 3 shows an example in which the NAND circuit 35 is realized by using a quad 2-input NAND gate (74HC00).

  When the card travel signal shown in FIG. 4A changes to active (low level), the first monostable multivibrator 31 sets the first pulse width t1 accordingly, as shown in FIG. 4B. Having a preliminary reset signal.

  The second monostable multivibrator 32 generates a reset mask signal having the second pulse width t2 when the preliminary reset signal from the first monostable multivibrator 31 changes to a low level. The second pulse width t2 is set to be longer than the time necessary for the F2F demodulator 13 to perform the discarding operation.

  As shown in FIG. 4D, the NAND circuit 35 outputs a reset signal that becomes a low level when both the preliminary reset signal and the reset mask signal are at a high level.

  According to the above configuration, when the reset mask signal is at a low level, no reset signal is output even if the preliminary reset signal is at a high level. Therefore, the F2F decoding unit is not reset again when the second read-out is completed.

  As described above, in the magnetic card reader according to the present embodiment, when the F2F demodulator 13 discards a predetermined number of bits, the F2F demodulator 13 resets it once, and again reads the predetermined number of bits into the F2F demodulator 13. As a result, the analog signal can be demodulated without being affected by noise.

  Next, a second embodiment of the present invention will be described.

  The magnetic card reader according to the present embodiment is the same as the magnetic card reader of FIG. 1 except for the internal configuration of the reset circuit 15.

  As described in the background art section, when noise exists in the head portion of the analog signal, after the F2F demodulator 13 finishes the discarding operation, the output data signal immediately changes to a low level. Therefore, the reset circuit 15 of the magnetic card reader according to the present embodiment monitors the clock signal and the data signal output from the F2F demodulator 13 after the end of the discarding operation for a predetermined time, and within a predetermined time after the end of the discarding, for example, It is detected whether or not the data signal changes before the first clock rise.

  More specifically, when an analog signal as shown in FIG. 5A is input to the F2F demodulator 13, the F2F demodulator 13 receives the clock signal and data signal shown in FIGS. 5B and 5C, respectively. Output to the reset circuit 15.

  If there is no noise at the beginning of the analog signal input to the F2F demodulator 13, a high level data signal is input to the reset circuit 15 as indicated by a broken line in FIG. However, when noise is present, the data signal changes to a low level at an earlier stage than the normal state, as indicated by a solid line in FIG. Therefore, the reset circuit 15 counts the clock pulses, and determines that there is noise if the data signal changes to a low level until the predetermined clock pulses are counted (within a predetermined time). Is output to the F2F demodulator 13.

  As described above, in the magnetic card reader according to the present embodiment, the F2F demodulating unit 13 is reset only when it is determined that there is noise within a predetermined time after the first discarding operation. .

  In the present embodiment, even if the number of bits of the preamble is not sufficiently larger than the number of bits to be discarded, the reset can be executed when noise is present.

  In the above description, the clock signal is used to determine whether or not the data signal changes to a low level within a predetermined time. However, the card running signal and the data signal are monitored, and the card running signal is low. After changing to the level, it may be determined whether the data signal changes to the low level within a predetermined time. Also in this case, the presence or absence of noise can be determined within a predetermined time after the first read-out operation is performed as described above. In this case, a counter circuit using another clock (system clock) or a timer of a microcomputer can be used to measure the predetermined time.

1 is a block diagram showing a schematic configuration of a magnetic card reader according to a first embodiment of the present invention. It is a signal waveform diagram which shows the input signal to the F2F demodulator used for the magnetic card reader of FIG. 1, and its output signal. It is a circuit diagram which shows the structure of the reset circuit used for the magnetic card reader of FIG. FIG. 4 is a signal waveform diagram for explaining the operation of the reset circuit of FIG. 3. It is a signal waveform diagram for demonstrating operation | movement of the reset circuit used for the magnetic card reader based on the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the conventional magnetic card reader. It is a wave form diagram which shows an example of the analog signal output from a magnetic head when normal magnetic recording information is read. It is a wave form diagram which shows an example of the analog signal output from a magnetic head when reading the magnetic recording information with partial demagnetization. FIG. 9 is an enlarged waveform diagram of the top portion of the analog signal in FIG. 8. It is a wave form diagram which shows the input signal without noise to the F2F demodulator of the conventional magnetic card reader, and its output signal. It is a wave form diagram which shows the input signal with noise to the F2F demodulator of the conventional magnetic card reader, and its output signal.

Explanation of symbols

10, 60 Magnetic card reader 11, 61 Magnetic head 12, 62 Amplifying unit 13, 63 F2F demodulating unit 14, 64 Decoding unit 15 Reset circuit

Claims (7)

In a magnetic card reader equipped with a demodulator for demodulating an analog signal obtained by reading magnetic recording information recorded in the F2F format with a magnetic head,
A reset that resets the demodulator when the demodulator performs a synchronization process using a predetermined number of bits from the beginning of the analog signal , and then performs a synchronization process again on the analog signal input to the demodulator A magnetic card reader characterized by providing a circuit. The magnetic card reader according to claim 1 ,
The reset circuit is
The demodulator resets the demodulator according to the level change of the card running signal whose level is changed when the predetermined number of bits are synchronously processed from the head of the analog signal , and then the card running until a predetermined time elapses. A magnetic card reader characterized by being configured not to respond to a change in signal level. In a magnetic card reader equipped with a demodulator for demodulating an analog signal obtained by reading magnetic recording information recorded in the F2F format with a magnetic head,
After the demodulating unit synchronously processes a predetermined number of bits from the head of the analog signal, the demodulating unit is reset when it is determined that there is noise before a predetermined time elapses , and then input to the demodulating unit A magnetic card reader, characterized in that it is provided with a reset circuit for performing synchronization processing on analog signals again . The magnetic card reader according to claim 3 ,
The reset circuit is
After the demodulator performs synchronization processing using a predetermined number of bits from the beginning of the analog signal , the noise is detected when the level of the data signal output from the demodulator changes before the predetermined time elapses. A magnetic card reader configured to reset the demodulator. In a method of reading a magnetic card having magnetic recording information in F2F format,
Converting the magnetic recording information into an analog signal;
When the demodulator performs a synchronization process using a predetermined number of bits from the beginning of the analog signal , the demodulator is reset, and then the synchronization process is started again for the analog signal input to the demodulator. A method for reading a magnetic card. In a method of reading a magnetic card having magnetic recording information in F2F format,
Converting the magnetic recording information into an analog signal;
After a synchronization process using a predetermined number of bits from the beginning of the analog signal in the demodulator, if it is determined that there is noise within a predetermined time, the demodulator is reset, and then the analog signal input to the demodulator A method of reading a magnetic card, wherein synchronization processing is started again for a signal . The method for reading a magnetic card according to claim 6 ,
A method for reading a magnetic card, comprising: performing synchronization processing using a predetermined number of bits from the beginning of the analog signal, and detecting that there is a change in the level of the data signal within a predetermined time, and determining that there is noise and resetting the magnetic card .

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