IBM 727 Manual Of Instruction Download

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The load-point reflective spot is sensed and R25 picks. Relay 25-3n /c points

open, dropping R12. Relay 1 2 -ln /o points open, dropping +48 volts to manual r e
verse and manual start. This causes the tape drive to stop setting in a loaded con
dition.

23.2

MANUAL CONTROL OF TAPE MOTION

The following section deals with the manual control of tape motion, using the

customer engin eers switch and the load-rewind button.

With the C .E . switch set to FORWARD GO, +48 volts is available to pick R27

from R 12-5n /c, RIAU n/o, R 1 3 -ln /c , C .E . switch, R 6A Ln/c, R 5ALn/c, R 15-4n /c,
to the R27 coil. In this case, +48 volts is blocked from "manual reverse" by diode

D5.  Relay  2 7 -ln /o   closes  to  bring  up  the  manual  start  line.  The  up  level  on  man
ual  start  conditions  the  top  leg  of  AND  circuit  T03JF27F  (76. 05. 01).  The  bottom
leg  is  conditioned  by  "not  arriving  at  load  point."  The  resulting  up  level  from   F27F
carries  through  OR  circuit  T03JE29F  and  brings  down  the  stop  line  through  inverter

T03J7B. Tape starts feeding in a forward direction at this time.

The plus shift on the start line is also fed to the bottom leg of AND circuit

T04JG20F (76. 04). An up level results from G20F because the top leg is condi

tioned by "At L . P . " This up level causes relay driver T04J5B to pick relay 26.
Relay 2 6 -ln /o closes to furnish +48 volts to the R25 latch trip coil.

Relay 25 returns to normal and the R 25-4n/o points open to bring down "At

L . P . " to AND circuit G20F (76.04). This results in a down level to the relay

driver T04J5B, allowing R26 to fall.

With the C .E . switch set to stop, R27 is allowed to fall. This brings down the

manual start line and the tape is stopped.

With the C .E . switch set to BACKWARD GO, +48 volts is applied to the manual

reverse  line  through  the  2 5 -ln /c   and  the  9 -3 n /c  points.  Relay  27  is  picked  through
the  diode  D5,  R6A Ln/c,  R 5A Ln/c,  and  R 15-4n /c  points.  Conditioning  the  manual
reverse  line  causes  the  tape  to  drive  backward,  from   the  right  reel  to  the  left  reel.

Turning the C .E . switch to stop brings down "manual reverse" and "manual start",

causing the tape to stop again.

Depressing the load rewind button conditions the lower leg of AND circuit

T03JB30F (76. 08). The top leg is conditioned by read status and the resulting up

level causes relay 21 to be picked by relay driver T03J4B. Relay 2 1 -ln /o points

close to pick R3 and R3BUn/o closes to pick R9. Relay 12 is picked because of

the R 9-5n/o points closing and it is held by the R 12-2n/o points through diode D2.

The load point reflective spot being read causes R25 to be latch picked, R 25-3n /c

opens to drop R12. Relay 1 2 -ln /o opens to drop R27 and +48 to the manual reverse
line. The tape drive stops, setting in loaded condition with the load-point reflective

spot under the photo cell.

23.3

TAPE MOTION UNDER CALCULATOR CONTROL

Tape motion can be controlled from the computer programming. A control

0002 instruction in the 705 CPU causes the start rewind line to condition the upper

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