[amsat-bb] DireWolf config file question

I'm trying to set up the config file in Direwolf. The radio is a Yaesu FT290RII and the interface is a Signalink USB. The Direwolf manual says this about setting up the PTT configuration:

#

# If not using a VOX circuit, the transmitter Push to Talk (PTT)

# control is usually wired to a serial port with a suitable interface circuit.

# DON'T connect it directly!

#

# For the PTT command, specify the device and either RTS or DTR.

# RTS or DTR may be preceded by "-" to invert the signal.

#

#PTT COM1 RTS

#PTT COM1 -DTR

#PTT /dev/ttyUSB0 RTS

Unfortunately, I don't know what that means. Anybody know which one I should use? Any hints, tips, suggestions would be much appreciated.

Steve Kristoff AI9IN EM79ji Oldenburg IN skristof@etczone.com