created a separate thread for the Televideo 910 terminal discussion.
Connected a terminal up to it this afternoon, settings are:
19200, 8, N, 1
plug is DB25 female but wired as DTE meaning
pin 2 is TxD (out)
pin 3 is RxD (in)
pin 4 is RTS (out)
pin 7 is signal ground.
Manual is here.