60
Basic circuit diagram of door entry system installa-
tion with speech privacy, for use in buildings with
three entrances.
Alcad multiple entrance systems are based on the
use of microprocessor-controlled audio units (micro-
processor-based 4+N system). Rather than using
changeover switches to select one of the entrance
panels, the audio unit has been fitted with a micro-
processor that decides which entrance panel should
be activated, and deactivates the rest of the panels
in the system.
This system simplifies the cabling of the installation,
reduces the number of components and improves
system operation.
Telephones with the privacy of conversation featu-
re remain inactive until they are called from the
entrance panel. Until a call is received the dwelling
telephone is disabled. It is therefore not possible to
listen to conversations between other tele-phones and
the entrance panel.
Operation
One of the entrance panels in the system is chosen
to be the main panel just one panel per installation
can be defined as the main one. To select it, remove
jumper J1 from the other entrance panels. The main
panel is the one which is connected by default to the
system’s telephones. The other panels are only acti-
vated when one of the call buttons is pressed.
When a call button is pressed, the corresponding
panel comes on to allow communication with the
telephones. The system busy indicator light on the
other panels will start to flash to indicate that they are
disabled.
When one of the push buttons on one of the
entrance panels is pressed the electronic call signal
generated by the audio unit (7) is sent via the call line
to the corresponding telephone (5), where it is heard
on the loudspeaker of the handset. At the same time
the audio unit’s own loudspeaker generates a sound
to confirm to the visitor that the call has been made.
The audio unit also generates a control signal (17)
that deactivates the other entrance panels.
The telephone that receives the call is activated by
connecting its electronics internally to the common
wire (2) and the door lock release wire (1). While
the telephone is activated it is possible to open the
door or communicate with the caller by picking up
the handset. Once the call is received, the audio unit
starts a 30 second timer while it waits for the tele-
phone handset to be picked up. If the handset is not
picked up during this time, the control signal (17) is
removed and all three panels go into the standby
state.
If during this time the handset is picked up the elec-
tronics associated to the telephone’s audio lines (3
and 4) is internally connected to the entrance panel.
This connection sets up the communication between
the telephone and the entrance panel. The audio unit
starts a fresh 60 second period before disabling the
telephone and removing the control signal (17), pu-
tting all three panels into standby state. When only
10 seconds are left a buzz will be heard. It is possi-
ble to restart the timer either from the entrance panel,
by pressing the push button, or from the dwelling
end, by pressing and releasing the telephone hand-
set’s hook switch. After finishing the communication,
when the audio unit detects that the telephone hand-
set has been hung up, it removes the control signal
(17) and all three panels go into the standby state.
When the door lock release button on the telepho-
ne is pressed, the audio unit of the active panel
detects the closing of the lock release circuit (1). The
audio unit then sends an a/c voltage (11 and 12) to
the electric lock connected to the active entrance
panel, thus allowing the entrance door to be ope-
ned.
The common wire (2) of the telephone and entran-
ce panel provides the return path for all the telepho-
ne signals. The common wire is connected while the
telephone is active.
THREE ENTRANCE INSTALLATION WITH ELECTRONIC CALL
AND PRIVACY OF CONVERSATION
MICROPROCESSOR-BASED 4+N SYSTEM
To Next Page
Loading...
Need help?
General
