Open network operations, Introduction, Intelsat business system (ibs) – Comtech EF Data SDM-300A User Manual
Page 257: Chapter 10. open network operations
10–1
Chapter 10. Open Network
Operations
10.1 Introduction
This chapter summarizes the functionality and specifications of the various Open
Network operating modes (IBS, IDR, Drop & Insert, and G.703).
10.2
Intelsat Business System (IBS)
IBS operation adds a proportional overhead (1/15) to the terrestrial data. The terrestrial
data and clock are passed through the baseband loopback relay and are translated from
the selected baseband format to Transistor-Transistor Logic (TTL). The data is scrambled
synchronously with the multiframe sync in the multiplexer. The scrambler is enabled
using the front panel.
External input and output for an ESC in EIA-232 format is provided on the interface. The
ESC runs asynchronously at approximately 1/2000 of the terrestrial data rate. If the ESC
clock is used, the channel runs at 1/512 of the terrestrial data rate. The overhead
containing framing, the ESC channel, and faults from the modem are multiplexed with
dejittered terrestrial data. The multiplexed data stream is output to the modulator through
the interface loopback device.
The receive data from the demodulator is input through the same interface loopback
device. The receive data is demultiplexed and synchronously descrambled by the
demultiplexer. The backward alarm is reported to the M&C and output by Form C relay
contact. The ESC is output by an EIA-232 driver. The terrestrial data output from the
demultiplexer is input to a plesiochronous buffer.