The EL4XXA series are solid state relays containing an Al GaAs infrared LEDs on the light emitting side (input side) optically coupled to a high voltage output detector circuit. The detector consists of a photovoltaic diode array and MOS FETs on the output side. The single channel configuration i s equivalent to 1 form A EMR. They are packaged in 4 pin DIP and available in surface mount SMD option.