These optocouplers consist of one gallium-arsenide light-emitting diode and one silicon npn phototransistor per channel. The TIL191 has a single channel in a 4-pin package, the TIL192 has two channels in an 8-package, and the TIL193 has four channels in a 16-pin package. The standard devices, TIL191, TIL192, and TIL193, are tested for a current-transfer ratio of 20% minimum. Devices selected for a current-transfer ratio of 50% and 100% minimum are designated with the suffix A and B respectively.