Comtech EF Data SDM-300L3 - Manual (Page 259)

10–1
Chapter 10. OPEN NETWORK
OPERATIONS
10.1 Introduction
This section summarizes the functionality and specifications of the various Open
Network operating modes, such as:
• IBS
• IDR
• Drop & Insert (D&I)
• 2xADPCM Voice in 64 kbps IBS
10.2 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.