Vehicle Speed Sensor

What type of signal does a VSS produce?  Is is the same signal as the signal coming from the speedometer sensor on the wheel?

Here's why I ask:

I'm installing a deck on my motorcycle that has speed compensating volume.  In order to get it to work, it needs to be attached to the VSS and I''m not sure if my bike has one.  Since my bike has an electronic, not cable-driven, speedometer, I'm considering splicing the VSS lead from the deck into the line that takes the pulse from the rear end to the speedo.

Does it make sense to try this? I don't want to screw up the deck but, more importantly, I don't want to screw up my speedometer.

Thanks for your input.

I have a '90 BMW K75RT.  The speed sonsor is on the rear end inside the drive shaft gearing. 

Fortunately, there's a coupler in the line before it reaches the the instrument panel so I plan to tap into it there and not have to mess around with taking apart the instrument console.

What will a diode do? Since the signal from the sensor is most likely a sine wave, won't it just cut half of the signal off?

Have you done this before?

Update:

I found a tehcncial support guy at a company that makes VSS-related products.  I figured I'd find someone who really knew his stuff.  After an email discussion with him, I tapped in to the lead from the speed sensor (before it goes to the computer) to the head unit autosound lead and the autosound feature is now working.