The Expandable ZX-80 and ZX-81

Hardware Projects for the Sinclair ZX Mini Computer for the Hobbiest by a Hobbiest

In the modern computer are a number of small electronic packages by which contain hundreds and even thousands of semiconductor devices all designed to either turn something on or something off. These are called Integrated Circuits. Some, however, are designed to amplify sound or voltages, and these are known as linear devices.