Appeal 2007-1535
Application 10/626,969
Boreham discloses a siren unit 2 with a CPU 4 that provides signals
that activate an audible siren responsive to trigger signals received on
control input 10 via serial interface 12. The control input 10 is connected to
a vehicle security control unit that is able to (1) monitor the vehicle, (2)
determine when an alarm condition occurs, and (3) issue the appropriate
trigger signal (Boreham, col. 2, ll. 41-53; Fig. 1).
Depending on the siren unit’s configuration, the siren unit is triggered
in either of two ways: (1) the contents of a control data packet received by
the serial interface 12, or (2) a trigger signal on the control input 10
(Boreham, col. 4, ll. 28-31). If serial interface control is enabled, the CPU
must regularly receive (e.g., every second) a 24-bit control packet 54 from
the vehicle security control unit to prevent the siren from being activated
(Boreham, col. 4, l. 55 - col. 5, l. 12).
The details of this 24-bit control packet are provided in the table in
column 5 and Figure 6. Significantly, a four-bit address field is provided
(Bits 0-3) which enables the vehicle security control unit to address devices
other than the siren unit 2 on a single serial data bus (Boreham, col. 5, ll. 15-
60; col. 6, ll. 20-23; Fig. 6).
Although the exact extent of this serial data bus is unclear from the
reference, Boreham nevertheless provides some indication of the ability of
the vehicle security control unit to communicate with vehicle devices other
than the siren unit. The vehicle security control unit can generate a warning
signal by causing an LED on the instrument panel to flash (Boreham, col. 7,
ll. 14-23). Moreover, in an alternative embodiment shown in Figure 8, the
vehicle security control unit can monitor the state of the ignition line 28 and
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