Those were peripherals.. H10 paper tape punch/reader or the H8-5 Serial I/O card (Cassette). They didn't have a card reader at first, just paper tape and cassette. I ran CP/M on mine, but its been a loooooong time :-) Take a look at the wikipedia article.. it has more than I remember about it!
Discussion
Nice!! 256 bytes.
My first was some years later with the Apple II+
because it had 64k instead of 48k
Had the Hayes Micromodem II
Capable of 150 AND 300 baud!! 😆
We ran up a $750 phone bill on the Computer-Serv network in a month and it hit the fan when my poor parents got the bill.