Seriously, thanks for the info on that cable, Only Apple would come up with such a silly, expensive way to avoid implementing a switch on the cable or making a simple dongle. At least it's not another massively protruding connector like the PowerBook cables.
There actually was a _very good_ reason they did it that way. Alas, since I have no idea how much anyone here knows or does not know about the hardware parts of vintage RS-232 stuff, I'll have to go into a bit of boring background detail before I can plainly explain why:
RS 232 style connections were bodged together so that random important pieces of equipment, which needed data connections but could not be kept next to the room a mainframe was in, could connect in a consistent way to the communication gear that made the distance feasible. For practical purposes, every "232-serial" line has a modem on one end and a piece of actual useful equipment on the other; respectively, they are formally called the "Data Communications Equipment" (DCE) and the "Data Terminal Equipment" (DTE).
That's an important point. 232-serial connections were defined purely as a dedicated interface to a telecom adapter. (Had it been done 25 years later, there might well have been an underlying assumption that the modem would be on an internal expansion card of some sort, instead of a separate unit tethered by a cable.) In those early days, the idea of using a 232-style link to join equipment of equal importance would have been nonsensical; generally, if the things were that close together, there were better methods to employ.
Long story short, 232-style connections started out very much a one-sided arrangement; the data could go both ways, but one end of the link was very obviously more important than the other. The result? All the pins in that DB-25 shell are named the same on both ends: "Transmit Data" carries data out of the DTE, and _into_ the DCE.
Next part of this is, while the _signals_ involved were standardized in the 1960s, the hardware was not. That D-25 connector and the arrangement of signal pins within it were more or less accidental - they were a de facto industry norm by the time anyone tried (and, naturally, failed) to standardize it. No one should be surprised that the few pins relevant to Apple II users were not at all conveniently positioned from one another.
The third needful data fragment: Conceptually, a null modem is literally an empty box with two 232-serial connectors. They're cross-connected inside the box, so that (for example) the "Transmit Data" signal on each of them is routed to the "Receive Data" signal on the other, and so on.
Putting all that together, a "null-modem cable" merely does the crossing-over inside the connector at one end, so rather than two serial cables and an empty box, you just have the one cable.
Here's where I actually address the topic I'm replying to: Normal and crossover 232-serial cables are not remotely similar on the inside. Building a cable with a single switch that reroutes half-a-dozen or more connections at once would have been vastly more expensive than what they did do, in simply tossing a normal crossover (null-modem) cable in with the regular straight-through one.
