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Connecting the exchange lines
2.1.9
CAUTION
Do not connect the exchange lines until the 2+8 has been subjected to
a pre-connection inspection.
Feed the exchange line cable(s) through the CCU cable entry hole and
terminate the A and B wires on the IDC terminals marked A and B on the
main printed circuit board.
Connecting extension bells/tone callers
2.i.10
A high impedance extension bell or tone caller may be connected to an
extension. The cabling and wiring procedure is the same for connecting
extensions (see paragraph 2.1.8) except that additional two-wire
cabling/wiring will be needed from the master jack to the extension bell
position. Connect the bell across the master jack IDC terminations pin
numbers 3 and 5.
External extensions
2.i.11
The 2+8 system is approved for external extensions providing the
extension instrument is within the confines of the customer's premises
and the system's operational limits. See Section 10.1, Statutory
information.
Care should be taken when selecting external cable routes to ensure that
the cabling complies with current wiring regulations and that exposure to
high voltage surges is kept to the minimal.
Protection of the CCU and telephones against high voltage surges is
recommended where extensions and external cabling are likely to be
subjected to induced high voltage surges such as lightning (for example,
overhead spans). The provision of protection is at the discretion of the
system maintainer and should be agreed before acceptance testing.
Protection can be in the form of a gas discharge tubes (GD1) (protectors
21A) fitted across each pair of wires and to earth. These should be
mounted in a box connection 200 series or any other approved type of
box connection offering similar protection. The protection should be
installed at each end of the external cabling or as specified in any current
installation practises on external protection.
TPU 1371 Issue 3 (4/91)
Installation procedures
2-8
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