A data communication system comprises a portable device for effecting radio communication,
a communication adapter card for storing therein a plurality of communication protocols
corresponding to a plurality of communication systems employed by the portable
device, a computer in which the communication adapter card is inserted to execute
data processing, and a connector cable composed of a first connector connected
to the portable device, a second connector connected to the communication adapter
card for outputting identification information to identify one of the communication
systems employed by the portable device, and a cable for connecting between the
first and second connectors.