Table 709: Line data communication module
Characteristic Range or value
Type of LDCM Short range (SR) Medium range (MR) Long range (LR)
Type of fiber Graded-index
multimode
62.5/125 µm or
50/125 µm
Singlemode 9/125
µm
Singlemode 9/125 µm
Wave length 850 nm 1310 nm 1550 nm
Optical budget
Graded-index multimode
62.5/125 mm,
Graded-index multimode
50/125 mm
13 dB (typical
distance about 2
mile *)
9 dB (typical
distance about 1
mile *)
22 dB (typical
distance 50 mile *)
26 dB (typical distance 68 mile *)
Optical connector Type ST Type FC/PC Type FC/PC
Protocol C37.94 C37.94
implementation **)
C37.94 implementation **)
Data transmission Synchronous Synchronous Synchronous
Transmission rate / Data
rate
2 Mb/s / 64 kbit/s 2 Mb/s / 64 kbit/s 2 Mb/s / 64 kbit/s
Clock source Internal or
derived from
received signal
Internal or derived
from received signal
Internal or derived from received
signal
*) depending on optical budget calculation
**) C37.94 originally defined just for multimode; using same header, configuration and data format as C37.94
19.2.18 Galvanic X.21 line data communication (X.21-LDCM)
19.2.18.1 Introduction
The galvanic X.21 line data communication module is used for connection to
telecommunication equipment, for example leased telephone lines. The module
supports 64 kbit/s data communication between IEDs.
Examples of applications:
• Line differential protection
• Binary signal transfer
1MRK505222-UUS C Section 19
IED hardware
1125
Technical reference manual
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