Digital trainers integrate a breadboard with simple I/O and they are a great tool to learn digital circuits. DIGILAB-R is a vintage style digital trainer designed to be compatible with the Scuola Radio Elettra DIGILAB. It can be used to perform all the experiments in the Digital Electronics distance learning course that was popular in the 80's.
The schematics is divided in sections to implement all the different functions.
The quad NAND U2 acts as a debouncer for P1 and P2. The clock generators are implemented with a simple RC oscillator driven by the schmitt trigger inverter U1. The toggle switches and the edge detectors (D type flip-flop U3) are wired directly to the output connector.
For the hexadecimal display the original DIGILAB used a pair of TL311. These are nowadays very hard to find. Our team opted to implement the display using a standard 7-segment display paired with a vintage MC14495 decoder.
Buffering for the single LEDs has been implemented using a octal inverting buffer (U4).