The FSIP provides four or eight channel-independent, synchronous serial ports that support full-duplex operation at T1 (1.544 megabits per second [Mbps]) and E1 (2.048 Mbps) speeds. The ports are divided into two 4-port modules, each of which is controlled by a dedicated Motorola MC68040 processor and contains 128 kilobytes (KB) of static random-access memory (SRAM). Each module can support up to four T1 or three E1 interfaces, and an aggregate bandwidth of up to 6.132 Mbps at full-duplex operation.The FSIP4 has one module for ports 0-3, and the FSIP8 has two modules, one for ports 0-3 and the other for ports 4-7. To provide a high density of ports, the FSIP uses special port adapters and adapter cables. A port adapter is a daughter board that provides the physical interface for two FSIP serial ports. Each FSIP comprises an FSIP board with two or four port adapters. (One module is equivalent to two port adapters.) Additional port adapters are available as spares so that you can replace one that fails; however, you cannot upgrade a 4-port FSIP to an 8-port FSIP by adding port adapters. (The 4-port FSIP is not constructed to support additional ports after it leaves the factory; it contains the circuitry to control only one 4-port module.) An adapter cable provides the network connection for each port and determines the electrical interface type and mode of that interface.