| 摘要 |
An improved alarm system for monitoring movement through a passageway defined by opposing sidewalls. The alarm system has a lower passage indicator disposed toward the lower ends of the sidewalls, an upper passage indicator disposed toward the upper ends of the sidewalls and a control mechanism configured to sound an alarm if the lower passage indicator indicates passage through the passageway and the upper passage indicator does not. In one embodiment, each of the passage indicator comprises transducers that are configured to direct and receive sound waves, such as ultrasound waves, and provide lower and upper ultrasound waves that act as lower and upper barriers. If only the lower barrier is interrupted, indicating a child passing through the passageway, the control mechanism will generate an alarm signal. If both barriers are interrupted, indicating an adult passing through the passageway, the control mechanism will not generate the alarm signal. |
| 主权项 |
1. An alarm system for a passageway defined by a first sidewall and a second sidewall, said alarm system comprising:
lower passage indicator means disposed generally toward a lower end of the first sidewall and generally toward a lower end of the second sidewall for indicating passage through said passageway by a child or an adult, said lower passage indicator means configured to transmit sound waves across said passageway; upper passage indicator means disposed generally toward an upper end of the first sidewall and generally toward an upper end of the second sidewall for indicating passage through said passageway by the adult, said upper passage indicator means sufficiently spaced above said lower passage indicator means so as to not indicate passage through said passageway by the child, said upper passage indicator means configured to transmit sound waves across said passageway; and control means operatively connected to each of said lower passage indicator means and said upper passage indicator means for determining whether passage through said passageway is by the child or by the adult, said control means configured to generate a signal when passage through said passageway is by the child and to not generate said signal when passage through said passageway is by the adult. |
