Vmesnik za nalaganje programov na ZX81 preko SD kartice.
ZXPAND+ ZX81 Timex 1000 SD card interface Zxpand
https://www.sellmyretro.com/offer/details/zxpand%252B-zx81-timex-1000-sd-card-interface-zxpand-63279
Sinclair ZX81 ZXPand User Manual
https://archive.org/details/manualzilla-id-6899695/page/6/mode/2up
