Compaq 1610 Reference Manual page 18

Your handheld PC is equipped with many convenient features
that make using it quick and easy. This section familiarizes you
with the location and function of these features.
Screen
Modem
connector
PC Card slot
Displays on-screen information and
interprets stylus taps.
Connects an RJ-11 modem cable
(available on some models only).
Accepts a 16-bit Type I or Type II PC
(PCMCIA) Card. For more on this
feature, see Chapter 6, "Using PC
Cards."