IBM Series 1 User Manual page 109

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Periodic or aperiodic interrupts--external
The timer generates periodic or aperiodic interrupts,
but timer start and stop is controlled by the external
gate when the timer is in the run state.
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The timer card is plugged into any I/O position of a 4955 or
4953 Processor or any position of an I/O expansion unit.
There is no limit to the number of timer cards that can be
used in a system.
There is an optional filtering capability of the
customer digital input lines brought into the timer card.
This option is selected with jumper wires on the component
side of the timer card either for TTL input or filtered TTL
input. The location of the jumper wires is illustrated in a
subsequent section of this chapter (see Figures 3-2 and
3-4) •
3-2 GA34-0033
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