Abstract: A probe which mounts in a liquid container has a conductance electrode containing a temperature sensor. A conductance control circuit is coupled to the probe to control an output relay in accordance with predetermined impedance conditions at the probe, and a temperature limit control circuit also controls the output relay in accordance with predetermined temperature conditions at the probe.

Abstract: A sequencing blow down or blow off valve mechanism for the low water cut off and/or water column of the equalizing piping network of a steam boiler. The valve mechanism is located at the junction of the vertical cut off outlet pipe, the lower horizontal pipe to the boiler and the vertical drain line. The valve mechanism normally rests in a position completing the network while blocking the drain line. The valve mechanism may be moved to successive positions completing drain paths from the lines of the network to the drain line. Whenever the valve mechanism is out of the normal position, the fuel supply to the boiler is shut off to prevent boiler firing. The valve mechanism provides a visual indication of the valve position. Further the valve mechanism allows access to the network lines for cleaning and/or rodding of the lines whenever the valve mechanism is in any of the successive positions. Manual and automatic operation are disclosed.