Pit-level indicator:

One of a series of devices that continuously monitor the level of the drilling mud in the mud tanks.

The indicator usually consists of float devices in the mud tanks that sense the mud level and transmit data to a recording and alarm device (a pit-volume recorder) mounted near the driller’s position on the rig floor.

If the mud level drops too low or rises too high, the alarm sounds to warn the driller of losing circulation or a kick.