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Common night service. The operator presses button N2 on her console before
going off duty. The lamp lights in that button.
Incoming calls are signalled on one or more bells placed at strategic points
in the premises. The call can be answered from any non-restricted extension
by raising the handset and dialling the public exchange prefix. If the call is
not answered, it is cleared in the same way as under individual night service.
Automatic night connection is established if the operator forgets to press
either of the night service buttons.
Serial Calls
If a subscriber wishes to speak to more than one extension, the operator
presses the serial call button. She thereafter puts the call through to the first
extension in the usual way. When the conversation with the first extension has
been completed, FDR-C recalls the operator, who then connects to the next
extension. When the last conversation has been concluded the operator presses
a restore button and FDR-C is released.
Installation and Maintenance
Relay sets and switches are connected to the rack cabling via multipole
plugs. This means that all switching units can be easily inserted and removed,
which greatly assists testing and maintenance.
When the rack has been placed in its final position, the extension and
exchange line cables and the cable from the power equipment are connected
to easily accessible terminal blocks on the left-hand end of the rack. After
jumpering and strapping for extension categories have been completed in
accordance with the customer's desires, the relay sets are plugged-in. The
rack has multipole jacks for plugging-in of the operator's console.
The extension telephones are connected to the exchange on three wires, one
of which may be a common wire.
Technical Data
The operating voltage for AKD 735 is 48 V, but the exchange operates
satisfactorily between 44 V and 56 V.
Line Data
Extension line resistance: max. 1000 ohms including telephone set.
Insulation resistance between the two branches of a line or between one
branch and earth: min. 25,000 ohms.
Line resistance between push-button telephone set and positive terminal:
max. 400 ohms.
The line and insulation resistances of the exchange lines are dependent on
the performance of the public exchange.
Feed
The resistance of the feed coils is 2 x 400 ohms.