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fixed-line customer telephone Type Part No.
provider (analogue)
BXT ML4 BD HF 24 920 375
+ BXT BAS + 920 300
SDB
DRL 10 B 180 FSD 907 401
+ EF 10 DRL + 907 498
+ DRL HD 24 + 907 470
DLI TC 2 I 929 028
DSM TC 2 SK 924 272
DG M TNS 275 952 400
S 2m
SFL PRO 6X 912 250
NT 1)
NTPM telecom. system 1) Network Termination
Figure 9.14.3 Surge protection for telecommunication systems with “ISDN primary multiplex connection”

Surge protection for the ADSL connection Surge protection for the ISDN connection
In addition to a conventional telephone connection, an ADSL ISDN (Integrated Service Digital Network) offers different ser-
connection requires a network or ATM card in the PC (depend- vices in a common public network. Both voice and data can be
ing on the type of access), a special ADSL modem and a splitter transmitted via digital transmission. The transfer interface for
to separate the telephone and data traffic. The telephone con- the NTBA, which is also supplied with 230 V a.c. on the power
nection can be an analogue or ISDN connection. supply side, is a network termination unit.
Figure 9.14.2 shows surge protective devices for an ISDN
The splitter divides the analogue voice signal or the digital connection.
ISDN signal from the ADSL data taking into account all impor-
tant system parameters such as impedances, attenuation and Surge protection for the primary multiplex connection
level. It thus fulfils the function of a dividing network. The split- The primary multiplex connection (NTPM) features 30 B-chan-
ter is connected to the telephone socket on the input side. On nels with 64 kBit/s each, a D-channel and a synchronisation
the output side, it provides the high-frequency signals of the channel with 64 kBit/s and allows data transfer rates up to
ADSL frequency band to the ADSL modem and controls com- 2 MBit/s. The NTPM is supplied by the U 2m interface. The device
munication with the NTBA or the analogue terminal device in interface is referred to as S 2m . Large-scale interphone systems
the low frequency range. or data connections with high data volumes are connected
The ADSL modem is connected to the PC via an Ethernet to this interface. Figure 9.14.3 shows surge protective de-
(10 MBit/s), ATM25 or USB interface and requires a 230 V a.c. vices for such a connection. The NTPM is also supplied with
supply voltage (Figures 9.14.1 and 9.14.2). 230 V a.c. on the power supply side.

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