2.4.4
Surge Protection
High voltage surge protection is provided in the system. To utilise this
surge protection circuitry a
telecommunications earth must be provided to the terminal marked ETH on the outside of the main
equipment.
In lightning prone areas exchange lines and two-wire extensions must be protected at the point of entry or
distribution in accordance with TPH 0265N0 “Lightning Protection at Customers Premises” and TPH
02 16 “LSA Plus Terminating System”.
For this protection to be effective an earth must be supplied to the SDF, the resistance of which should be
as low as possible and must not be greater than 30 ohms.
2.4.5
Earth Recall
When the system is connected to a PBX and the recall facility is required, the PBX earth must be connected
to the ER connection via the SDF.
2.4.6
Stations
When cabling from the main equipment to the stations take care that the pairs are correctly terminated and
the polarity of the pair is correct. The equipment will not operate if the system is not correctly cabled. The
order in which stations are connected and the station number are important when assigning powerfail
stations.
The connections between exchange lines and stations during power failure are fixed as follows:
Exchange Line No.
Station No.
The station cabling is as follows:
WIRE
6 0 5 PLUG/61 0
DESIGNATION
SOCKET
AL1
2
AL2
6
BD+
1
5
WIRE COLOUR
WT White
BL Blue
RD Red
BK Black
2.4.7
Table 2.4.6
STATION CABLING
Powerfail Bell
10
11
14
15
18
23
DESIGNATION
IN STATION
LWT
LBL
LRD
LBK
When installing a power-fail bell, connect the wires from the bell to terminals
and
the main
equipment, corresponding to line x.
2.4.0
Call Metering Unit
A B LA LB
A B LA LB
T O S D F
TEL ECOM
EXCHANGE
TELECOM
EXCHANGE
LINE
LINE
A B LA LB + E
TO SDF
TELECOM
EARTH
EXCHANGE TO
LINE
M.E.
Fig. 2.4.8 CALL METERING UNIT WIRING
46
AN-61 6
ISSUE