| 24 Line I/O Port | Controlled using BASIC, with suitable interface circuits will control LEDs, motors, relays, lights, sound generators. | Timex/Sinclair 1000 |
| Digital to Analog Converter | Fits onto input/output port to give one analog output (0 to 2.55 volts); space on board for two extra converters. | Timex/Sinclair 1000 |
| Keyboard | Full-size 40 key keyboard. Symbols marked in two colors. | Sinclair ZX80, Timex/Sinclair 1000 |
| Motherboard | Plugs into the back of ZX81 or ZX80. Printer/RAM pack plugs onto back. Has two female connectors to accept expansion boards. | Sinclair ZX80, Timex/Sinclair 1000 |
| Timer/Counter/Music Board | Three programmable counters. Controlled in Basic. May be used as timer, counters, or frequency generators (including audio range). | Timex/Sinclair 1000 |
