Chapter 1. Introduction
7
November 2001
Master timing
The ETU-01A E1 link receive path always operates on the
receive clock. The ETU-01A recovers the receive clock from the
received E1 link data signal. The source of the ETU-01A E1 link
transmit clock may be selected by the user. The following E1 link
transmit timing modes are available:
• Recovery timing:
The ETU-01A E1 link transmit clock is locked to the
recovered receive clock. This is usually the timing mode selected
for network operation.
• Internal timing:
The ETU-01A E1 link transmit clock is derived from the
internal clock oscillator. This timing mode is necessary in point-to-
point applications over leased line. In this case, one ETU-01A
must use the internal oscillator, and the other may operate from
the recovered clock.
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