This is an opto-isolator for controlling large loads of current on a single channel. This 4-pin dip can be used in conjunction with relays, small motors, etc. to allow a simple microcontroller to turn on and off up to 50mA. Sold as individual units. https://elecena.pl/product/633869/optoisolator-1-channel-hcpl-817 2008-04-21 https://elecena.pl/product/633869/optoisolator-1-channel-hcpl-817 2008-09-23 https://elecena.pl/product/633869/optoisolator-1-channel-hcpl-817 2008-10-18 https://elecena.pl/product/633869/optoisolator-1-channel-hcpl-817 2013-06-07 https://elecena.pl/product/633869/optoisolator-1-channel-hcpl-817 2014-02-06