Motorola's Surfboard cable modems are one of the most popular series on the market. Numerous models are available to suit the needs of various Internet Service Providers, or ISPs. These devices act as the bridge between a user's home or business Local Area Network, or LAN, and the cable Internet network, also referred to as the Wide Area Network. Their role is to transform the signals transmitted to the larger network from digital packets to an analog stream at the provider's specified frequency and voltage level. The modem also translates the incoming analog stream into packets the user's computer network can understand.
The primary components of a cable modem are as follows:
SYSTEM-ON-CHIP PROCESSOR (also known as SOC)
This is a single integrated circuit that provides all the functions of a low-end computer, including the microprocessor, random access memory, operating system, configuration parameters, and network interface hardware to communicate with both the local and wide area networks. Two common manufacturers of this SOC are Broadcom and Conexant. SOCs exist in multiple varieties with different processor types and quantities of memory. These SOCs usually run a small, embedded version of the Linux operating system.
ANALOG-DIGITAL CONVERSION HARDWARE
This hardware is responsible for converting the signals used on a Local Area Network in the Ethernet standard to the analog standard used by cable Internet networks, and the reverse. For example, Surfboard cable modem will usually bridge LANs to the DOCSIS 2.0 or 3.0 network standards, or the EuroDOCSIS equivalents outside of North America. A different standard is used due to differences in power and video frequency for consumer electronics such as cable televisions and computers.
This portion of the cable modem provides connectivity via one or more RJ-45 jacks to an Ethernet network. This 8-pin interface typically uses unshielded twisted pair cable for interference cancellation. The interface can be connected to an individual PC, or to a wired or wireless router for communication with multiple computers on a network. Communication can also be established to mobile phones, PDAs and tablet computers.
This interface connects to the cable Internet network via the same coaxial connector used by cable television. It is sometimes connected to the modem after a splitter with an in-line attenuator.
This component is an AC to DC current adapter, also known as a "power brick". It sits between the modem and a power supply, usually line current from an outlet. It converts 115 volts AC or 230 volts AC at 60 or 50 hertz to a DC voltage level with no frequency, typically at or below 12 volts. It also provides regulation to keep the current supply steady.