[WriteLog] cw keying, com port

[Tom Sessions]

When configured for "PC Generates" CW on a COMM port, WriteLog sends CW on
the DTR line of the COMM port.

    The above was taken from the help section of Writelog.  Would someone
please further clarify it for me?  I measure -5.5 VDC between pin 4(DTR) and
pin 5(GND) of my selected DB9 com port with no keying going on.
    Does the help explanation mean that WriteLog will key dits and dahs at 0
VDC with -5.5 VDC in between?  Does it mean WriteLog will key dits and dahs
at +5.5 VDC with -5.5 VDC in between?  Or are there some inverse or other
key up/ keydown voltages?

    In essence, what I am asking is what is the DTR pin voltage for "key
down", and what is the same DTR pin voltage for "key up" ?

Thanks
Tom K4RV