| CPC E21B 3/02 (2013.01) [E21B 7/046 (2013.01); E21B 19/083 (2013.01); E21B 19/165 (2013.01); E21B 44/02 (2013.01)] | 3 Claims |

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1. A horizontal directional drilling machine comprising:
a rotational drive unit having an output member configured to connect with and selectively drive rotation of a drill string when the rotational drive unit is in a first mode, the output member of the rotational drive unit configured to be rotated by the drill string when the rotational drive unit is in a second mode;
a vise operable to clamp two consecutive drill rods of the drill string for threading or unthreading by the rotational drive unit;
an operator input device that allows an operator to select between the first and second modes of the rotational drive unit; and
a control system including a controller connected for signal communication with the rotational drive unit and the operator input device, wherein the control system is configured to, in response to receiving an input to the operator input device to change from the first mode to the second mode:
direct the rotational drive unit into the second mode when the vise is unclamped; and
direct the rotational drive unit into a suspend mode when the vise is clamped, the control system automatically directing the rotational drive unit from the suspend mode into the second mode upon unclamping of the vise.
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