RFL SMX3 / 21
Page 7 of 22
Issue 1.4
User Manual
08 June 2009
The DCE configuration may be used in specific circumstances where signal timing
from the network timing is unavailable (e.g. when used with a radio link that does not
provide a clock source). Two alternatives are:
The timing source is derived from a co-located unit that is itself deriving the
master clock signal from the network. The two units are interconnected via the
concatenation link (refer to following section. In this case Clock Source must be
configured to Concat Port.
The timing source is derived from within the unit; in this case the Clock
Source must be configured to Master.
In both cases the timing signal is output on pins 6 and 13.
Optional X.21 Port Pin-out (when in DCE configuration) – D15M on chassis
Circuit
Pin A
Pin B
Direction
Notes
T Transmit
Data
2
9 Input
R Receive
Data
4 11 Output
C Control
3 10 Input
Signal
ignored
I Indication
5 12
Output Permanently
on
S Signal
Element
Timing
6
13
Output
Timing signal derived from
the port and transmitted to
network
G Ground
8 15
Screen / Drain
Must be earthed to shell
In either configuration, use 6 pair plus ground stranded cable with overall shield
(eg RS 111-8994).
Maximum recommended length in substations - 10m (Check Utility standards).
DIP switches provide configuration options, see section 10.
