Simple Line Current Detector Circuit Diagram

This is a simple Line Current Detector Circuit Diagram. This circuit will detect line currents of about 250 mA or more without making any electrical connections to the line.Detection of line-current flow and indicating the flow to an electrically remote point is required in line status monitoring at a variety of points in the Telephone system and auxiliary systems. The line should be minimally unbalanced or loaded by the monitor circuit, and relatively high levels of 60-Hz induced voltages must be ignored. 

 Simple Line Current Detector Circuit Diagram

The H ll A Al allows line currents of either polarity to be sensed without discrimination and will ignore noise up to approximately 2.5 mA. In applications where greater noise immunity or polarity- sensitive line-current detection is required, the HllAlO threshold coupler can be used. This phototransistor coupler is specified to provide a minimum 10% current transfer ratio at a defined input current, while leaking less than 50 p.A at half that input current over the full -55°C to + 100°C temperature range. The input current range, at which the coupler is on, is programmable by a single resistor from 5 to 10 mA.