| 2K Memory Upgrade | Kit to increase the ZX81 to 2K. | Sinclair ZX81 |
| CFASTDATA | Provides all of the capabilities of CIOUTIL, but 6 times faster. Writes data to cassettes and reads data from cassettes at a speed which is 6 times faster than the TS1000/ZX81 SAVE and LOAD commands. | Timex/Sinclair 1000 |
| CFASTDUET | CFASTDATA and CFASTLOAD. When both programs are used, you may LOAD programs and data at a speed which is 6 times faster than the TS1000 and ZX81 LOAD and SAVE commands. CFASTLOAD can be configured to your needs. | Timex/Sinclair 1000 |
| CIOUTIL | Utility to selectively read and write strings and arrays to a cassette. Routines occupy approximately 500 bytes and require at least 2K RAM. | Timex/Sinclair 1000 |
| Edge Connector | Many vendors sold ZX80/ZX81/TS 1000 compatible edge connectors in solder-tail and wire-wrap versions. The wire-wrap connector could be used with a small printed circuit board to build a feed-through device that would allow for connecting another expansion unit. | Timex/Sinclair 1000 |
| RS232/TTL Level Converter Plans | Construct an RS232/TTL level converter from inexpensive components. This converter, when used with the Cosmonics TTL Serial Input/Output Port Package, allows connecting a TS1000 or ZX81 to most RS232C peripherals. | Timex/Sinclair 1000 |
| Serial Input Port Plans | | Timex/Sinclair 1000 |
| Serial Output Port Kit | Plans and parts to build a serial output port using two integrated circuits. Plans also available separately. | Timex/Sinclair 1000 |
| Software for Serial Input | Provides RS232 input timing and ASCII to Sinclair character translation. | Timex/Sinclair 1000 |
| Software for TTL Serial Output Port | Provides correct RS232 timing and translation to ASCII. | Timex/Sinclair 1000 |
| TTL Serial Input/Output Port Package | Software and plans for building input and output ports which fit inside a ZX81 or TS1000. When used with an RS232/TTL level converter, can connect to most RS232C peripherals. | Timex/Sinclair 1000 |
