A drill rig includes a drawworks having a drum operably connected to a drive system and a brake. A drill string extends from the drum of the drawworks, along a derrick, to a block and tackle arrangement holding a travelling block so that operation of the drawworks causes the drum to release or retract the drill string. A travelling block controller controls the operation of the drawworks. An interlock sensor senses a sensed parameter, and the sensed parameter is at least one of a drill rig parameter, a drawworks parameter, or a travelling block controller parameter. An interlock signal generated by the interlock sensor is reflective of the sensed parameter. An interlock operably connected to the travelling block controller receives the interlock signal and disables operation of at least one of the travelling block controller or the drawworks if the interlock signal meets a predetermined criteria.