Hitachi 670 Series Application Guide

5.6.6.2 Service settings for transceiver 21–219
GUID-F8C098BE-407F-4281-951C-BE4AB476C2AA v1
Only one setting is required for transceiver 21–219. It has to be set to internal or external clock
depending on the configuration of the telecommunication network. Clock synchronization
configuration using the rotary switch can be done on the fly.
When transceiver 21-219 port is synchronized from the SDH master clock (transceiver acting as
slave), transceivers at both ends of the line are configured to use an external clock. To achieve this,
the rotary switch on the transceiver's front panel is set to point to position 0 (LEDs 1, 2, 4 and 8 are
not lit).
When the PDH/SDH is port synchronized from transceiver 21-219 (transceiver acting as master), the
local end transceiver is configured to use the internal clock. To achieve this, the rotary switch on the
transceiver's front panel is set to point to position 1 (LED 1 is lit and LEDs 2, 4 and 8 are not lit).
5.6.7 Earthing
GUID-3321FABA-BC02-4367-BE8F-92C2D37796E5 v1
The interface protection circuitry in transceiver 21-219 requires that the SDH multiplexer (SDH MUX)
interface is either directly or via low resistance connected to the same earth as the earthing screw on
the transceiver's front panel. There is no overturned protection in transceiver 21-219. If there is
potential difference between transceiver 21-219 earth and SDH MUX earth, current can flow in the
outer shield of the connecting cable. This may damage the cable and degrade the system
functionality resulting in bit errors.
The outer shields of the coaxial cables must be earthed to the chassis via the BNC contacts at both
ends as shown in Figure
87.
IEC07000158-1-en.vsdx
Transceiver
21-219
TX
RX
SDH
MUX
RX
TX
BNC contacts with the
screen connected directly to
chassis (earth)
Make sure the boxes are
properly earthed with shortest
possible connections to, for
example, an earthed frame
Important: power supply
from the same battery
Earthing
screw on
front
Coaxial cables
< 10 m
IEC07000158 V1 EN-US
Figure 87: Earthing principles
1MRK505382-UEN Rev. K Section 5
Communication set-up
Communication set-up, 670/650 series 85
Application Guide
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Hitachi 670 Series Specifications

General

Brand	Hitachi
Model	670 Series
Category	Control Unit
Language	English