Opto card for universal PC I/O interface

Whenever an interface is connected to a circuit with a supply voltage higher than 5 V, there is the risk that an error during experimenting, or a faulty component, will cause serious damage to the computer system. The opto card described here has been designed to afford complete electrical isolation between the computer and the (cruel) outside world, which is the only way to prevent system down time and expensive repairs caused by incompatible signal levels.