Hi, new to the list...and wondering if anyone has any ideas about an issue I'm having with a Model 43 KSR with TTL board, hooked up to an S-100 computer, in this case a Vector Graphic, from the laste 70's.

I am going through a DB25 null modem, so handshaking is there along with the correct pin assignments, yada yada. The Altair correctly prints out the monitor prompts to the Model 43 and I'm able to issue commands to it from the Teletype, as well as receive back the correct data. The data received back from the computer looks fine and characters aren't doubled.

A problem arises when I type in commands from the 43. Characters are repeated, eg, typing 1234 will yield 11223344. I'm not sure what is causing this.

An interesting thing is that when I communicate to my PC's terminal program, from the 43, the doubling of characters doesn't occur. On that I have it set to 7 data bits, Even parity, 1 stop bits.

Currently, both machines are set to 300 baud. On the 43 I have Parity Off and on Full Duplex. I'm not sure if the problem is on the computer or Teletype side.

Thanks for your input,

Jon