TRS-SO
MODEL III
Asynchronous transmission over a simple twisted wire paircan be accomplished at
moderately high baud rates
(10K baud orhigher, depending on the length
of
wire,
type
of
drivers, etc.). Transmission over the telephone network is generally limited
to approximately
2K
baud and a modem is required to convertthe data pulses to
tones that can be transmitted through the telephone network. Radio
Shack's
Telephone Interface is the ideal modem for this RS-232""C Interface.
Signal Conventions
The
E.I.A.
RS-232-C
electrical specification defines voltage levels and corresponding
logic conventions associated with data and control information transmitted
between equipment. Fordata interchange, the signal is considered in the
marking
condition when the voltage measured at the interface point is more negative than
- 3 Volts(with respect to signal ground). The signal is considered in the spacing
condition when the voltage is more positive than +3 Volts(with respect to signal
ground). The marking condition corresponds to a logic one
(1) and the space
condition corresponds to a logic zero
(0). Fortiming and control interchange
circuits, the function is considered to be "on" when the voltage on the interchange
circuit is more positive than
+3 Volts(withrespect to signal ground); and is
considered to be
"off"
whenthe voltage is more negative than - 3 Volts(with
respect to signal ground). The"
on"
condition corresponds to a logic zero (0) and
the'
'off'
' condition corresponds to a logic one (1). The following table summarizes
this information.
INTERCHANGE
VOLTAGE
NOTATION
Negative Positive
Binary State
1
0
Signal Condition
Marking Spacing
Function
OFF
ON
Table.
On/Off
Condition
1/2
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