scope:

This specification contains the technical requirements of the Federal Aviation Administration (FAA) for a modular, general purpose, multiple channel, digital communications multiplexing modem with integrated fiber optic transmit and receive functions (hereinafter referred to simply as multiplexing modem). When three or more of the multiplexing modems specified herein are integrated, as in a network, the network shall have the capability to "drop-and-insert" digital communications channels at any one of up to eight locations. (The total number of channels shall not be required to exceed 32.) The multiplexing modem specified herein shall, in conjunction with a Network Monitoring System (NMS) provide the capability to remotely control and diagnose a network comprised of the same. Modules are specified which satisfy the interface and signal requirements of NAS-MD-790 and the land line/telephone line circuits of the four-wire modems of the airport surveillance radar model ASR-9, FAA specification FAA-E-2704B. These units are intended for use as the principal element in a fiber-optic-based signal distribution system for airports.