Simons Voss Technologies SmartRelay 3 Manual page 12

5. System description
SmartRelay 3 system (Manual)
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NOTE
Follow the switch-on sequence
After a power-on reset (power outage followed by restoration of power
supply), the controller automatically searches for connected system com-
ponents one time on restarting. System components which are not sup-
plied power until the controller restarts are thus unable to respond to the
controller's query and are not recognised.
The controller must therefore be supplied power with the other system
components at the same time or must be the last system component to
receive power.
5.2 Reader
At least one external reader is required to use the SREL3 ADV system.
SmartRelay 3 readers are ordered separately from the controller.
The controller is unable to read identification media. Up to three readers
can be connected via an RS-485 interface for this purpose. They can read
both active and passive identification media. After reading media, the
readers transmit the data to the controller, which checks the identification
medium's authorisation and triggers relevant actions as programmed. The
reader itself is unable to trigger actions and can thus be installed in less
protected areas. In the WP variant, the housing is sealed and protected
against splashing water.
Readers can either be powered through the controller or equipped with
their own power supply unit.