I'm successfully using a Protege PC-LINK that was purchased at Big-Lots for $9.99. This unit came with case, spare stylus, instruction manual, software (CD-ROM), and cable/adapter. The latter consist of a cable with an electronic interface built into the serial port's connector: I suspect that it's proprietary. The electronic circuitry is simple and elegant.

First I installed the software (Friendly-Sync Databank V2.0) on my desktop machine. Upon trying to establish a Protege to PC link experienced a popup window (Data Sync Message) "Data Sync is Timedout!". Under DOS, I ran AMI Diagnostics' Serial test, with the provided loopback plug, which failed on both COM 1 and COM 2, external loopback error. Hardware problem!

Then I installed the software on a legacy laptop, Toshiba 445CDX, and it all worked as advertised. So did the external loopback test.

Summary: I've use a Magellan GPS with the desktop's COM ports sans problem; but not so the Protege. I ran into a similar problem circa 1986 with some AST machines we had purchased. The vendor shipped them with a noname serial card that couldn't pass AST's diagnostics. At the time we only used the serial ports for mice and these devices work OK. But I felt uncomfortable because sooner or later someone would try to use these ports for something else: Which would fail. Anyway, I persuaded the vendor to send genuine AST replacement cards. This solved the problem.

Philosophy: Like people not all hardware is created equal. My mentor (Doc Jones), now departed, used to say "Some people are more equal than others" :-)