Comtech EF Data SMS-451 - Manual (Page 19)

SMS-451 Sateliite Switch Revision 0
Introduction MN/SMS451.IOM
1–5
1.1.2 SMS-451E Description
MANUAL
AUTO
ON-LINE FAULT
MODULATOR
A
A A
B B B
MANUAL
AUTO
ON-LINE FAULT
DEMODULATOR
A
A A
B B B
REM O T E
R E M
L O C A L P W R 1
P W R 2
SWITCH STATUS
L O C
SMS-451E ECL MODEM
PROTECTION SWITCH
Figure 1-4. SMS-451E
The SMS-451E 1:1 ECL Modem Protection Switch (Figure 1-4) is a fully automated 1:1
ECL protection switch for the Comtech EF Data SDM-9000 satellite modem.
IMPORTANT
ECL/HSSI connection also is available for the SDM-2020 Modems.
The switch is used to protect SDM-9000 modems using an ECL, Positive Emitter
Coupled Logic (PECL), or MIL-STD-188 terrestrial interface. The switch provides
redundancy for one prime modem with one backup modem.
The switch contains circuitry for:
• Data and IF switching
• Remote and local status reporting
• Remote and local control
The switch can be supplied with any of the following baseband interfaces:
• ECL
• PECL (positive level ECL)
• MIL-STD-188
The switch top assembly has the following configurations:
Operation Input Frequency Interface
Modem
(Dependent) AC 75 Ω 70 ECL
Mod/Demod
(Independent) AC 50 Ω 140 PECL
DC 50 Ω 188
DC 75 Ω