26 Oct
2012
26 Oct
'12
1:22 p.m.
One particular scheme "evolved" due to the
structured cabling being
shared between telephone and serial terminals - the serial stuff was
put on pairs not used by the phones, so as to reduce problems caused
by users plugging things into the wrong socket...
Avoid pins 4 and 5 for the serial port, that pair is commonly used for a
single telephone line.
Haiving ringing voltaeg (around 75-100V AC) appear between RS232 port
pins can really ruin your day.
-tony