IBM 1710 Manual page 58

Interrupt and Process Branch Indicators
The Interrupt and Process Branch Indicators are not
assigned terminal addresses, nor are they connected to
the process via a standard or thermocouple terminal
block connection. They connect through smaller termi-
nal s trips. An ex ternal (process) or internal (I 71 0)
occurrence turns on its associated indicator (Interrupt
or Process Branch) . The indicator must be interrogated
by a Branch Indicator or Branch No Indicator instruc-
tion before any action can result.
58
Parity Checking
The contents of
TAS
and the Function Register are
parity-checked for invalid characters and parity errors.
A parity error or invalid character in
TAS
will turn on
the
TAS
Check indicator (21), but with one exception:
the terminal addresses 300-399 will not cause a
TAS
Check. A parity error or illegal character in the Func-
tion Register will turn on the Function Register Check
indicator (22).
Whenever either of these two indicators is turned on,
the program instruction is blocked so that an erroneous
operation will not occur.