BT BF900 - Manual (Page 58)

57
Technical information
You may connect it –
• To direct exchange lines.
• To extensions with new plug and socket
arrangements provided with these direct
exchange lines.
• To compatible switchboards.
You may NOT connect it -
To shared (party) lines.
The connection to the telecommunication
system must be unplugged before the earth
is disconnected. The connection to the
telecommunication system must not be
hardwired.
This apparatus may be used on
telecommunications systems employing loop
disconnect or MF signalling.
How many phones can you have
Your exchange line provides only a small
current to make your BF900 ring. Although
you may have any number of sockets it is
important to limit the number of telephones
and other items of apparatus connected to the
line by these sockets. This ensures that each
telephone will receive enough current to ring.
Every telephone or item of apparatus has a
Ringer Equivalence Number (REN).
In most cases a standard line should provide
enough current for two or more telephones or
items of apparatus, if the REN’s add up to no
more than 4.
BF900 has a REN of 1. Any telephone provided
by BT may be assumed to have a REN of 1
unless otherwise stated on the base. Even
where the number of telephones has been
limited, there is no guarantee that the different
types of telephone on the same line will ring.
The provided handset must only be connected
to the socket on the side of the machine.
Another approved handset may be connected
but the apparatus has been calibrated and
approved for the provided handset.
The voltage drop introduced by the apparatus
between the PSTN and a series connected
telephone at a current of 40mA is 1.7 Volts.
Consequently, no additional series equipment
may be connected.
The introduction of this voltage drop may
occasionally cause difficulties in making calls
from the series connected telephone or
problems in telephone conversation being
experienced by both parties to the call. In the
unlikely event of any such problems occurring,
the user should contact the supplier or
maintainer of the apparatus.
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.