The IBM PC Network was IBM's first LAN system. It consisted of network cards, cables, and a small device driver known as NetBIOS (Network Basic Input/Output System). It used a data rate of 2 Mbit/s.
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Broadband
The original broadband version in 1984 communicated over 75 Ω RG-11-type cable using frequency-division multiplexing, so traffic travelled on separate transmit and receive frequency ranges, using a Sytek head-end device to translate between the two signals, and it was intended that the cable be shared, with video and voice traffic using other bands. It ran at 2 Mbit/s.
NetBIOS was developed by Sytek Inc as an API for software communication over this IBM PC Network LAN technology; with Sytek networking protocols being used for communication over the wire. IBM's later token ring network emulated the NetBIOS application programming interface, and it lived on in many later systems.
Baseband
Later, in 1987 a much cheaper "baseband" version, also running at 2 Mbit/s connected computers in daisy-chain style using twisted-pair cables with RJ45 connectors and CSMA/CD. Interface cards had two RJ45 sockets for connecting to left and right neighbor nodes. The unused sockets at the ends of the network segment had to be fitted with terminators.