A simple decoder arrays to a for linking photocell microcomputer

Inputs from photocell arrays (such as those incorporated in mazes) to a microcomputer must be decoded. For up to 31 channels, this can be conveniently done by using cascaded 8-to-3 line priority encoders (74LS148) and five lines on a parallel data bus. The arrangement is expandable. It is currently used in an automatized Y-maze for vibrisso-tactile discrimination learning in mice.