On 2014-01-27 23:32, Don Latham wrote:
Mike S
On 1/27/2014 1:33 PM, Robert Atkinson wrote:
I looked at this a while ago. The "spec" only defines transmission
levels, it does NOT specify receive thresholds.
It certainly does...
"2.1.3 For data interchange circuits, the signal shall be considered in
the marking condition when the voltage on the interchange circuit,
measured at the interface point, is more negative than -3 volts with
respect to Circuit AB (Signal Common). The signal shall be considered in
the spacing condition when the voltage is more positive than +3 volts
with respect to Circuit AB (see 6.2). The region between +- 3 volts is
defined as the transition region. The signal state is undefined when the
voltage is in this transition region."
- ANSI TIA/EIA-232-F (1997)
wellll, maybe needed if you're running an ASR-33 teletype. . .
Except ASR-33s came with a 20ma current loop interface.
Later models added RS232 after it became popular.
ISTR TWX terminals required one and Telex terminals the other.
--
Take care. Thanks, Brian Inglis
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