Use the LTC (Longitudinal Time code) device to synchronize MotionBuilder to an external time code source. To activate the LTC as a time code source, you must add the LTC device, then select it as the reference time code source in the Timing Controls. You must have the LTC card installed to use the LTC device.
Add the LTC device and select the sound card connected to your computer from the InputDevice pull-down menu. The longitudinal time code automatically becomes the reference time code.
LTC device settings A. Select a sound card from the Input device menu
Once you have activated your LTC device, you can use the Time Code property in the Properties window. This property allows you to associate time code to animation by using the keyframe and animate buttons. 
LTC properties window A. Keyframe button B. Animate button