My TR(a)S(h) 80, Model 1 had a similar Boot technique. It would load Basic Interpreter and OS, plus whatever app you planned to use, via the "CLOAD" command. This would run an external tape deck (typical cassette deck), and load the above from the cassette tape.
Connection was done via "MIC" and "SPKR" panel mounted jacks.
Loading took forever!
This was the first Machine I found the extreme value of creating and Archiving Back-Up media!!!
Since Audio Tape is so prone to gaussing issues + other fun stuff, I got to experience the loss of Read data, and the effect it has when loading from those Audio Cassette Tapes!
Needless to say, everything was re-written, and copied back to _SEVERAL_ Cassettes!
On my Model 2, got a good crash course regarding the familiar Interrupt 80 (IRQ80h).
I believe this IRQ originally was to initiate loading of the Basic Interpreter from external Tape drive(s) on Machines???
Since the Model 2 had no "Fixed Disk Drive", it would stop at IRQ80 if there was no system disk placed in the first floppy disk drive (8" low density drive!).
Prompt was similar to IBM's, displaying:
"Non System Disk Or Diskette, Reboot"
Messed around with those Z-80 based Machines for a long time.
Got an actual PC in early 1993. Man, what a change!!!
Scott35