Comtech EF Data SDM-300A - Manual (Page 307)

12–1
Chapter 12. Asymmetrical Loop
Timing
12.1 Introduction
Asymmetrical Loop Timing is the same timing method that is designed into the
SDM-650B TROJAN interfaces. Refer to Figure 12-1 and Figure 12-2 for TX and RX
Asymmetrical Loop Timing block diagram. There are two advantages for using
Asymmetrical Loop Timing:
Versatility: The user selects different TX and RX data rates, yet still clock the send data
with the receive satellite clock.
Fits easily into on site
clocking schemes:
The user may clock the send data with a clock that is not necessarily
operating at the same rate as the data rate.
The send timing may only be referenced from an external clock source that is equal to the
data rate in the basic modem.
The asymmetrical clock loop reference must be one of the following:
• TX terrestrial clock
• External clock input
• RX clock input