British Telecommunications (BT) Senator, System Manual

Page: 34 / 75

CPE/MS
526
Issue
2 (12/88)
Part
6
POWER FAIL ARRANGEMENTS
No provision is made for standby power to maintain the operation of the
system if the mains power supply fails.
The relays in the CCU which normally perform the switching of the
extension and exchange lines are arranged such that when the power fails,
each exchange line is directly connected to certain extensions as follows (see
diagram overleaf).
Line
1
connects to extn.
1
and
6
Line
2
connects to extn.
2
and
7
Line 3 connects to extn. 3 and
8
Line 4 connects to extn. 4 and 9
Line
5
connects to extn.
5
and
10
Each extension will be able to make or receive calls on the exchange line
connected to it. The tone caller will operate to an incoming call but an
extension bell connected via a Bell Adaptor will not operate. When two
extensions are connected
to one exchange line, bell-tinkle will be
experienced at one telephone when the other dials.
Intercom calls cannot be made during mains failure, nor can calls be
transferred. Any programmed facility e.g. 'Divert' or 'Exchange Line
Ringing' will be cancelled and will need to be reprogrammed when power is
restored. There will be no visual indication (LEDs) during mains failure.
Short term power disconnections (between
100
milliseconds and
2
seconds)
may cause partial loss of customer-programmed facilities: these may be
corrected by turning the power off for
5
to
6
seconds to allow the
microprocessor to reset fully. When the power is restored the facilities
should be reprogrammed and checked.
Where external extensions are fitted, the adaptor will be reset to the remote
answer condition (lamp on).
6.1