At our editorial offices we are surprised (and delighted) how often we are being asked about relatively ancient circuits. In not a few cases, these circuits contain components that are currently no longer available, such as, for example, the 1 K size EPROM 2708, which required three(!) power supply voltages. The 2716 and 2732 are parts that are still reasonably easily obtained and programmed, and they also have 24 pins. These parts require only a single 5 V power supply.