MagTek P-SERIES TTL - Manual (Page 15)

Section 2. Installation
9
TIMING FOR BACK SENSOR AND CARD PRESENT
Figure 2-6 shows the timing for the Back Sensor and the Card Present signals.
The card is read in both directions (on insertion and withdrawal), but the data is active on
withdrawal.
Figure 2-6. Timing for Card Present and Back Sensor Signals
While it is possible for the Card Reader to read data on either the insertion or withdrawal stroke,
it should be noted that card reading is most reliable during the card withdrawal stroke. For this
reason MagTek recommends that customer’s software should be designed to emphasize data
capture during the card withdrawal stroke. For the most reliable operation: Read the card upon
insertion, when the card present goes high, check for errors, if no errors, output the data, start
sentinel first, after the card is withdrawn. If an error is detected, clear the stored data and read
the card on withdrawal, if no errors, output the data, start sentinel first, otherwise output an error
indication or a try again message.
ACTIVE DATA
MOST RELIABLE
ACTIVE DATA
NOTE 1
NOTE 1
NOTE 1
NOT TO SCALE
HEAD OUTPUT
SIGNAL
TIME OF INSERTION TIME OF WITHDRAWAL
INTERNAL CARD
PRESENT
BACK SENSOR
P/N 21065114
CARD PRESENT
AT CONNECTOR
Used on only
P/N 21065114
BACK SENSOR
P/N 21065117
NOTE 1:
Time out of the internal card present signal occurs approximately 150 ms
after the last strobe transition. The internal card present signal becomes
active when the movement of an encoded magnetic stripe past the read
head generates a signal. The back sensor and internal card present are
gated together to reduce the dwell time needed before the read-on-
withdrawal can be initiated and is output as card present at the connector.