PC-Network was a LAN

Local area network

A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

 system consisting of network card

Network card

A network interface controller is a computer hardware component that connects a computer to a computer network....

s, cable

Cable

A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...

s, and a small device driver

Device driver

In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

 known as NetBIOS

NetBIOS

NetBIOS is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, NetBIOS is not a networking protocol...

 (Network Basic Input/Output System). It used a data rate of 2 Mbit/s.

The original PC-Network hardware was available in two varieties, baseband and broadband.

The baseband

Baseband

In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...

 version connected computers in daisy-chain

Daisy chain (electrical engineering)

In electrical and electronic engineering a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring...

 style using twisted-pair cables with RJ45 connectors. 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 terminator

Electrical termination

Electrical termination of a signal involves providing a terminator at the end of a wire or cable to prevent an RF signal from being reflected back from the end, causing interference...

s.

The more expensive and less widely used broadband

Broadband

The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...

 version communicated over 75 Ω RG-11-type cable on separate transmit and receive frequency ranges, using a head-end device to translate between the two signals.

When the proprietary PC Network hardware was replaced by token ring in IBM's later offerings, backwards compatibility with the NetBIOS application programming interface

Application programming interface

An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

(API) was retained through an optional loadable program module.