The original Stern board has riveted optos, and it tends to fail.. you have to drill them out, desolder, and replace them. The remaining parts are surface mount, making repair even harder.
And when the board is in stock, it is $pricey!!
This replacement board has some very cool features to make your life easy. The optos are all installed with standard hardware. The leads come through the board UNSOLDERED, then solder to a pad on the board. This does two things.. it makes repair possible with a pencil iron. And it prevents vibration from shearing off the lead to begin with. Then, all parts are through hole, making it possible to repair with traditional methods.
And the finale.. there is a red and green LED for each channel.. The red is lit when the send LED is operating, and the green LED indicates when the opto is blocked/open. Makes troubleshooting a breeze.
The board is used on AC/DC next to a 3 channel version of the board.
And I warrant the board for 6 months. How can you go wrong?