48
Basic circuit diagram of door entry system insta-
llation in buildings with two entrances.
Alcad multiple entrance systems are based on
the use of microprocessor-controlled audio units
(microprocessor-based 4+N system). Rather than
using changeover switches to select one of the
entrance panels, the audio unit has been fitted
with a microprocessor that decides which entran-
ce panel should be activated, and deactivates the
rest of the panels in the system.
This system simplifies the cabling of the installa-
tion, reduces the number of components and
improves system operation.
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 panel. The main
panel is the one which is connected by default to the
system’s telephones. The other panel is only activated
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 panel will start to flash to indicate that it is disa-
bled.
When a push button 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 corres-
ponding 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
disables the other entrance panel.
The audio unit starts a 30 second timer while it
waits for the telephone handset to be picked up. If
the handset is not picked up during this time, the con-
trol signal (17) is removed and both panels go into
the standby state.
If the handset is picked up during this time, the
electronics 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
removing the control signal (17) and putting both
panels into standby state. When only 10 seconds
are left a buzz will be heard. It is possible to restart
the timer from the dwelling end by pressing and rele-
asing the telephone handset’s hook switch. After fini-
shing the communication, when the audio unit
detects that the telephone handset has been hung up,
it removes the control signal (17) and both 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.
TWO ENTRANCE INSTALLATION WITH ELECTRONIC CALL
MICROPROCESSOR-BASED 4+N SYSTEM
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