Heathkit H9 - TTY (20 mA current loop) Serial Input;Output; READER CONTROL

Page
16
TTY
(Passive)
Connections
-}
lzo
o
o
o
l/0
ctRcul
BOARD
PICTORIAL
2.'],O
TTY (20
mA
current
loop)
Serial
Input/Output
Passive
In
the
passive
configuration,
the
20
mA
loop
current
is
supplied
by
the
external
device.
pictorial
Z_tO
shows
the
jumper
wires
necessary
for
the
TTy (pas_
sive)
configuration
on the
I/O
circuit
board.
A
maik
is
defined
as
20
mA
flowing
in
the
current
loop.
A
space
is
defined
as less
than
4 mA
flowing
in
the
current
loop.
Pictorial2-1.1,
shows
the
partial
schematic
of
the
TTY
(passive)
wiring.
The
jumper
wire
that
disables
the reader
control
is
shown
in
pictorials
2-10
and
2-11.
Refer
to "Reader
Control"
on
page
1g.