Schmid Watson Installation Guide Page 22

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SZ-DOC-W5-1.pdf LTU/NTU
Version: 1.5 Operating Manual
13 Revision: 2002-09-10
External
clock
DSL
Tx
DSL
Rx
Recovered 2048 kHz Clock
2 Mbit/s Tx Clock
INP 2048 kHz
E1 Side DSL Side
E1
Tx
E1
Rx
Internal
Clock
2048 kHz
Clock-
Recovery
Stuff/
Delete
Figure 3-1: Clock Sources
Note:
Signals towards the transceiver section are denoted as Tx and signals coming from the
transceiver sections are denoted as Rx.
As long as the DSL link is not established, the internal clock oscillator is used as clock source.
The clock sources are automatically switched by the microcontroller, depending on the actual
signal and clock status, which is updated every 100 ms.
The transmit clocks of the two E1 data directions are independent of each other. Both
plesiochronous and synchronous operation modes are possible. Synchronous operation occurs
when the E1 equipment at one end of the DSL link uses the receive clock as transmit clock, as
shown below.
E1 NTU /
LTU
Tx
Rx
2048 kHz Clock
E1 Equipment
DSL
Tx
Rx
E1 Equipment
E1 NTU /
LTU
Figure 3-2: Synchronous Operation (=”Loop Timing”)
Warning:
Do not configure the E1 interfaces at both ends to use the receive clock as transmit clock except
if one DSL equipment is an LTU using the “External Clock” option. Otherwise there will be no
defined clock.
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