> can someone please let me know what type of signals travel along the
> qbus?

Roughly O.C. TTL, but with tighter specs:

Driver:
Vol: 0.7 V max at 70 mA
Leakage current: 25 uA max

Receiver:
Vil: 1.3 V max
Vih: 1.7 V min
Leakage current: 80 uA max

DEC used several different receiver, driver, and transceiver chips.
One of the most common was a DEC8641, which was a National DS8641
selected for tighter specs.  Later they used the DS3662, an improved
spec replacement for the DS8641, but they still apparently selected
them, since the DS3662 specs still don't meet the Qbus requirements.

National has end-of-lifed both the DS8641 and DS3662.  You can still
get them now, but possibly not for much longer.

I don't know of any current production (non-EOL) parts that meet
the Qbus specs.  You can get close for drivers using the 74ABT126,
tying the inputs to ground and using the enables.  To really guarantee
meeting the Qbus specs, you'd have to parallel two drivers.

The receiver specs are more troubling.  I'm not sure what to do other
than using a comparator.  In practice, normal TTL inputs will
probably work, if you don't worry about temperature extremes and
large configurations with multiple backplanes.