>From http://www.arcelect.com/rs232.htm:
RS232 data is bi-polar.... +3 TO +12 volts indicates an "ON or 0-state
(SPACE) condition" while A -3 to -12 volts indicates an "OFF" 1-state (MARK)
condition.... Modern computer equipment ignores the negative level and
accepts a zero voltage level as the "OFF" state. In fact, the "ON" state may
be achieved with lesser positive potential. This means circuits powered by 5
VDC are capable of driving RS232 circuits directly, however, the overall
range that the RS232 signal may be transmitted/received may be dramatically
reduced.
The output signal level usually swings between +12V and -12V. The "dead
area" between +3v and -3v is designed to absorb line noise. In the various
RS-232-like definitions this dead area may vary. For instance, the
definition for V.10 has a dead area from +0.3v to -0.3v. Many receivers
designed for RS-232 are sensitive to differentials of 1v or less.
http://www.lvr.com/serport.htm has many RS-232 links.
Steve, W1SRD
-----Original Message-----
From: writelog-admin@contesting.com
[mailto:writelog-admin@contesting.com]On Behalf Of Tom Sessions
Sent: Friday, July 12, 2002 2:39 PM
To: writelog@contesting.com
Subject: [WriteLog] cw keying, com port
When configured for "PC Generates" CW on a COMM port, WriteLog sends CW on
the DTR line of the COMM port.
The above was taken from the help section of Writelog. Would someone
please further clarify it for me? I measure -5.5 VDC between pin 4(DTR) and
pin 5(GND) of my selected DB9 com port with no keying going on.
Does the help explanation mean that WriteLog will key dits and dahs at 0
VDC with -5.5 VDC in between? Does it mean WriteLog will key dits and dahs
at +5.5 VDC with -5.5 VDC in between? Or are there some inverse or other
key up/ keydown voltages?
In essence, what I am asking is what is the DTR pin voltage for "key
down", and what is the same DTR pin voltage for "key up" ?
Thanks
Tom K4RV
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