The Telxon RFC330 was a Narrow Band RF Base Station, which provided Connectivity using an RS232 Serial Port to a host computer. Telxon provided API’s which could be used to write applications in C which would operate on one or more of the Telxon Portable Teletransaction Computers (PTC’s) and talk through the RFC330 to a host which was running on the host machine.
The RFC330 would operate on a defined frequency, which could be changed by substituting an internal component, and would typically connect to an omnidirectional antenna, either directly using a stub antenna on the top using the BNC type connection shown here, or externally using a long coaxial cable to a much larger external antenna mounted on a building.
Of course coverage could be extended by using more of the units, but frequencies could not overlap, and each RFC330 would need to connect to a separate port on a host, or a separate host, thus making larger deployments more complex. A typical PTC could connect to two different frequencies, meaning the RFC was not especially suited to massive scale deployments, and an RFC30 would be a better choice in this scenario.
I have a vague recollection that the RFC330 used an ETACS Radio, where the RFC30 used GTACS, but my memory of this is over 20 years old now, so I may be mistaken!