| 摘要 |
<p>PCT No. PCT/AU94/00754 Sec. 371 Date Sep. 5, 1996 Sec. 102(e) Date Sep. 5, 1996 PCT Filed Dec. 6, 1994 PCT Pub. No. WO95/16248 PCT Pub. Date Jun. 15, 1995A siren unit including control means for controlling activation of a siren loudspeaker (8) at a selected frequency based on a frequency control signal, and input means for providing the frequency control signal to the control means. The input means further provides a volume control signal and a duration control signal. The siren loudspeaker (8) is activated in response to a trigger signal received by the input means which may be a plurality of predetermined data bits. The siren loudspeaker (8) can be activated on the basis of a data communications packet received and provided by the input means. The siren loudspeaker (8) is also activated when the data communications packet is not received.</p> |
