7 Jan
2026
7 Jan
'26
11:20 a.m.
On Jan 7, 2026, at 12:47 PM, Richard via cctalk
<cctalk(a)classiccmp.org> wrote:
...
If you're really paranoid about damaging either the keyboard or the
terminal, you should use a voltmeter to identify which pins on the
connector are power and ground and make sure that they both the keyboard
you're going to try and the terminal agree on which pins are used for
power and ground. The remaining pins are going to be the serial transmit
and receive, likely at TTL levels not RS-232 levels.
I have no idea about non-DEC terminals, but the LK201 uses real RS232 levels. Those are
bipolar (plus or minus 5 volts or more) and if you connect that to a device with a TTL
input it may be unhappy. Typical TTL level logic devices object to negative input
voltages more than 1/2 volt or so.
You could look for the output pin on the keyboard connector of the terminal, ideally with
an oscilloscope at power up because it's likely to send some setup sequence. If you
see +/- 5 volt or so signaling, that would be RS232. If it swings between 0 and 4-ish
volts it's TTL and an LK201 would not work. You could use an RS232 transceiver chip
to convert the signal levels, that's easy. Or take my LK201 emulator with the RS232
transceiver omitted and replaced by a few jumper wires.
paul