RS232 - how to send DTR=ON?

I need to send the DTR (pin4) high.

This is my setup: Digital indicator -> RN220XP (RS232/bluetooth-dongle) -> BlueSMirf (RN44-BT)-> Arduino (uno or Mega).

The digital indicator needs a DTR-signal to send it's data.

  1. How do i achieve that in arduino?
  2. How can i do this from ie Teraterm.

Any ideas?