Yaw Damp in modern aircraft is a calculation in the FCC that constantly corrects rudder position, if you saw the rudder in flight it would look like it was fluttering constantly. Even in the 727 yaw damp is more or less a function of the auto pilot. If I remember older systems were less rate/gyro driven but simply tightened up rudder authority with airspeed hence the above statement about switching off on the 707 for t/o and landing.