There are two ways to connect a Macintosh Plus to AppleLine:
1) use the 590-0169A Cable and the Mini Din 8 to DB-9 Adapter.
2) use the A2C0311 590-0331-B Tan, or the A2C0312 590-0555-A Platinum cable.
These cables have a DIN 8 at one end and a 25 pin on the other, AppleLine
end.
Note: The second method has been shown to be generally more reliable than the
first.