TimeNuts@philipjackson.com said: > I'm wondering if something like this $10 item > http://www.nulsom.com/datasheet/NS-RS232_en.pdf That setup has a separate pin (hole?) for power. It's setup to expect Gnd, Tx, Rx, and Pwr from the TTL side. A previous message said the module designed for the job had a diode. I'd expect that is using power from one of the modem control signals. You could probably add a diode to make it work. > I don't know if I've seen an inverting one and that would seem a more costly > approach than handling the inversion on the clock board. Almost all TTL to RS-232 level shifter chips include an inverter. It's just historical. The first chips (MC1488, MC1489) did it that way and everybody who makes a new chip includes the inverter too so they can cleanly replace older chips. -- These are my opinions. I hate spam.