IBM Series 1 User Manual page 241

is used, some external non-IBM supplied power source must be
used to generate current for the receive current loop.
The equivalent circuit for the isolated contact sense inputs
is a series resistance between the input pins.
Non-Isolateg Contact Sense. Two connectoL pins are
available for the signal input. These inputs are used when
it is desired that the teletypewriter adapter card generate
current for the receive current loop.
The equivalent circuit for the non-isolated contact
sense inputs is a Lesistor
in
series with
a
voltage source.
II1.
One connector
pin
is available for TTL level
input.
The TTL input is non-isolated.
EIA. One pin is available for EIA RS232-C level input. This
input is non-isolated.
li£2unding. The cable shield ground wire must be connected
. to ·f.r~ 9,.£.QJ!!!Q.
a
t the point of en try in to
the IB
f1
enclosure. The cable shielded-ground wire must be connected
to
fil.!!~
ground at the userfs device end of the cable.
The performance of this interface may be affected
by
noise. Appropriate arc suppression, noise filtering, etc.
may be necessary on customer inputs.
Contact sense inputs are isolated from card ground.
TTL
and Ell signal ground is tied to logic ground in the
teletypewriter adapter card.
4-18
GA34-0033
f
(