IBM 1 Series - Driver;Receiver Information

Driver /Receiver Information
Inputs
Isolated Contact Sense. The user’s equipment must supply a current of 20
mA to the isolated contact sense inputs. This results in a voltage of
between +9.0 and +16.7 volts placed across the receive input terminals.
For a mask condition, the attached device must generate a current of 14
mA or greater. For a space, the device current must be less than 250 pA.
Nonisolated Contact Sense. The teletypewriter adapter can supply a current
of 20 mA to drive the receive current loop. The OEM driving source for
the receive inputs should be a passive device that can be approximated by
a resistor and a switch in series.
When the driving source switch is “open,” no current flows, and the
potential across the receive inputs is +24 volts +10%.
When the driving source switch is ‘“‘closed,”’ a current flows out of the
receive plus input and back into the receive minus input. The current flow
is I = 18.5 V/(910+R) where I=amperes, V=volts and R=ohms, and
where R is the impedance of the OEM driving source. R must be 400
ohms or less for reliable operation. For a mask condition, the attached
device must generate a current of 14 mA or greater. For a space, the
device current must be less than 250 wA.
EIA. The EIA ‘receive data’ signal input must conform to EJA
RS232-C/CCITT V.24 specifications. The input impedance of the ‘receive
data’ signal is 3 kilohms to 7 kilohms. This signal drives an SN75154 (or
equivalent) TTL receiver.
TTL. The TTL ‘receive data’ signal must be a TTL-compatible signal. The
input impedance of the TTL ‘receive data’ signal is 100 ohms. This signal
drives an SN75154 (or equivalent) TTL receiver, and draws 40 mA of
current.
4-26 GA34-0033