Abstract: A system for a pneumatically-actuated engine throttle of a snubber ram unit of an oil service/drilling rig, to stop accidental engine engagement of a pipe section and its being pulled into or pushed through the snubber ram unit of the rig, the system comprising a switch positioned in an air line between a pneumatic throttle control and an engine throttle of the rig, the switch manually actuatable between open and closed positions and normally biased towards open position, the switch associated with the throttle control and engine throttle, on the one hand, and a control for the snubber ram unit on the other, so as to override the throttle control and prevent actuation of the engine throttle when the switch is in closed position, the switch associated with the snubber ram unit control so as to be inoperative when the snubber ram unit is in an open position, but to be operative when the snubber ram unit is in a closed position, the switch constructed so as to require, when operative, manual positioning by an op