DLA / DLB Series NCC National Controls Corp Liquid Level Boards
This series of Level Controls provides high and low level sensing with Pump Up or Pump Down capabilities. The probe and sensing circuit are isolated from line voltage via a transformer. The probe is driven with and AC signal to prevent plating. The output is an electro-mechanical relay rated at 10 A.
In the Model DLA (Pump Down) the output relay is activated when the upper probe detects the presence of liquid and it remains activated and it remains activated until the lower probe detects the absence of liquid.
In the Model DLB (Pump Up) the output relay is activated when the lower probe detects the absence of liquid and it remains activated until the upper probe detects the presence of liquid.
If the tank is non-conductive a third (common) probe must be installed at a level where it will always be submerged.