Comtech EF Data SMS-758 - Manual (Page 18)

Introduction SMS-758 Modem Protection Switch
1–2 MN/SMS758 Rev. 3
The switch does not contain an IF signal combining/dividing section, so that the user
may externally tailor each application for minimum loss. An example system
configuration using four prime modems is shown in Figure 1-6.
In normal operation, each prime modulator input is fed through to its corresponding IF
output, and the backup modulators are fed to the offline IF outputs. When a modulator
fault is detected, the faulted modulator is switched offline and re-routed to one of the
offline IF outputs. The next available backup modulator is configured identically to the
failed modulator, and is switched ON in its place.
Figure 1-2 shows the switch interface between the prime and backup modems, the
terminal equipment, and IF converter equipment. The switch provides:
•
All data and IF switching circuitry
•
Complete status and fault reporting
The switch provides a high degree of flexibility by utilizing the multiple data rate feature
of the modems, and dual backups. Automatic configuration greatly reduces setup time.
1.3 Description
The switch is complete and self contained, in a standard 19” rack-mountable enclosure
weighing approximately 50 lbs. It is of modular construction. The chassis assembly is
segmented with upper and lower chassis mounted backplanes.
The top section (Figure 1-3) contains:
•
Two power supplies providing redundancy in case of power failure, four printed
circuit board (PCB) assemblies, and the front panel keypad and display, which
are accessible from the front of the switch.
•
Serial remote interfaces, relay-remote/fault, modulator and demodulator status,
and IF connections accessible from the rear panel. Figure 1-4 is a block diagram
of the IF switching matrix.
The lower section contains:
•
An enclosed storage area, accessible from the front panel.
•
The data switch interface modules, accessible from the rear.
The switch contains a microcontroller system. This system controls all switching
functions and maintains communication with the modems. It also communicates with an
optional external controller. A remote operator can control the switching by using a
terminal or computer, and the remote serial interface.