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400
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4-WIRE LEASED LINE 2400 BPS AND 4800 BPS
DATA SET AND LINE PROPAGATION
(INCLUDES ACKNOWLEDGMENT MESSAGE)
6
BIT--73MS (2400 BPS),O MS(4800 BPS)
8
BIT--79MS (2400 BPS), lOMS (4800 BPS)
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380
360
1\'
1\
0
\
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1\.,
20
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34
300
\
i\
60
\
40
\
20
00
180
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1\
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8
BIT
( 4800 BPS)'
6 Bit
(
2400
BPSI
8
BIT
(2400 BPS)
10
20
30
40
50
60
70
80
COLUMNS READ PER CARD
*USE THROUGHPUT FORMULA (FIGURE 7) TO
CALCULA TE 6 BIT THROUGHPUT RATE.
Figure 9.
IBM 2780 Card Reader Approximate Throughput Rate--Four-Wire Leased Line (See NOTE in Figure 7)
2780 terminal will attempt to punch the record but
will generate parity checks, send an EOT response
to the last block checking character, and sound the
audible alarm. Punching will be suspended for the
remainder of the card (short card record) when the
EM (End-of-Media) control character is received.
The EM character is punched, the card is released
immediately from the punch station, and another
card is fed (see discussion on card reading and
EM under End-to-End Control Characters in the
"Data-Link and End-to-End Control Characters"
section of this manual).
16
Reader and Punch Checking
Reader Checking
When reading cards, the following not-ready condi-
tions and reader checks result in transmitting an
STX ENQ sequence:
Card read/punch not ready
Operation of the stop key
Feed clutch --extra feed cycle
Equipment check
Data check
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