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Voltage drop
The voltage drop introduced by the apparatus between the PSTN
and the associated telephone/answering machine is 0.4 Volts at
40mA dc.
The introduction of this voltage drop may occasionally cause
difficulties in making calls from the associated telephone or
problems in telephone conversations being experienced by both
parties to the call.
While operation may be possible initially, changes to or
modernisation of the network taking place in the normal course
of events may result in the apparatus being connected to a
network service with which it is not designed to be compatible.
Failure of the apparatus to work under these circumstances may
not be the responsibility of the network operator.
In the unlikely event of any such problems occurring, the user
should contact the supplier or maintainer of the apparatus.
Difficulty may be experienced when making calls from other
apparatus. Such difficulties may include:
• difficulties in making a call;
• problems in telephone conversation being experienced by both
parties to the call.
Note - The definition of a RBS (Relevant Branch System) from
PSTN lines is given in BS6789 section 6.1 (1986) clause 2.4
Connecting to switchboards
Your DF450 is approved only for use with a compatible
switchboard including those which do not provide secondary
proceed indication.
If you do have a compatible switchboard, it cannot be guaranteed
that the DF450 will operate correctly under all possible
conditions of connection.
If you have any difficulties, contact BT on
Freefone 0800 800 152.
Safety warning
Interconnection circuits should be such that the equipment
continues to comply with the requirements of 4.2 of EN 41003 for
TNV circuits and 2.3 of EN 60950 for SELV circuits, after making
connections between circuits.
Interconnection directly, or by way of other apparatus, of ports
marked Safety Warning. See instructions for use. Ports marked
or not so marked may produce hazardous conditions on the
network. Advice should be obtained from a competent engineer
before such a connection is made.