Driver/Receiver Information - IBM Series 1 User Manual

Driver/Receiver Information
C
Inputs
c
o
Isolated
~ont~! .2~§g.
The user's equipment must supply a
current of between 20 and 60 mA to the isolated contact
sense inputs. This results in a voltage between 9.0 and
16.7 volts placed across the receive input terminals.
Non-Isola~g 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 t10%.
When the driving source svitch is "closed", a current
flows out of the receive plus input and back into the
receive minus input. The current flow is I
=
18.SV/(910+R)
where I=amperes, V=volts and R:ohms, where R is the
impedance of the OE~ driving source. R must be 800 ohms or
less for reliable operation.
~!!.
The EIA receive data signal input must conform to EIA
RS232-C/CCITT V.24 specifications. The input impedance of
the receive data signal is 3K to 1K ohms. This signal
drives an SN75154 (or equivalent) TTL receiver.
IT1.
The TTL receive data signal must be a TTL compatible
signal. The input impedance of the TTL receive data input
is 100 ohms. This signal drives an SN75154 (or equivalent)
TTL receiver. This input draws 40 rnA of current.
Outputs
&~~~! Qri~g~
(No Customer Supply Required). The
teletypewriter adapter card provides a current driver for
transmit output. The current driver provides the current to
drive the transmit loop. No external power supply is
required
if
this current driver output is used to drive the
OEM device receive input.
When the current driver is "on", a maximum current out
of the teletypewriter adapter card of 20 mA is generated.
The voltage across the transmit output pins when the current
driver is on is:
Vto = __
-R __
and tbe exact current flowing
620+R
Ito
=
12V
620+R
Teletypewriter Adapter 4-25