According to one Japanese source the PCE Modem, or Tsushin Booster, was released as a prototype to 20-30 PC Engine groups or fans, for monitored testing. After this, up to 100 ‘final’ units were produced before NEC pulled the plug and ordered them destroyed. The 20-30 early units were not recalled, and some of the 100 final units were spared, so with a run of anywhere between 30 and 130, the booster is possibly the rarest production PCE accessory.
Chris Covell has managed to find a PC Engine modem in Japan. He won’t say what he paid for it, but it was almost certainly a vast blow to his wallet. It was, however, a blow he took for all of us: he’s posted the details for everyone to enjoy. Everything’s up there: a look at the software, the documentation, and the hardware itself.
Surprisingly it’s a 300-1200 baud device, which at the time (early 1990s) was beyond slow. By this time in the real world 14.4k modems were available, more than ten times faster. Normal modems, however, didn’t come with groovy sprite editing software. On the other hand, with a PC and a normal modem you had a keyboard. Programming and communicating with a PC Engine pad was probably not fun for very long. For reference, here’s an old PC Engine Yahoo auction I saved.
[UPDATE] An anonymous donor has offered up the Tsushin Tool ROM for download. Grab your own copy!