Both ELS511 and ELS611 are SMD devices in a small outline 6-pin SDIP package. The ELS511 series devices each consist of an infrared emitting diode, optically coupled to a high speed photo detector transistor. A separate connection for the photodiode bias and output-transistor collector increase the speed by several orders of magnitude over conventional phototransistor couplers by reducing the base-collector capacitance of the input transistor. The ELS611 series devices consist of an infrared emitting diode optically coupled to a high speed integrated photo detector logic gate with a storable output.
Their dimensions of 9.7 x 4.58 x 3.38 mm, half of those of a 6N13X series (8-pin), greatly eases the use in designs with limited PCB area to make them suitable for space constrained industrial applications such as high speed ground isolation.