Sounder

1. A sounder that outputs alarm sound to notify an abnormality in a monitored region, the sounder comprising:

a sound source that outputs alarm sound when a pulse signal is applied to the sound source;

a pulse signal application unit that applies the pulse signal to the sound source; and

a storage unit that stores a plurality of combinations of a frequency and a pulse width that the pulse signal can take, wherein

the pulse signal application unit generates the pulse signal so that the pulse signal corresponding to the combination of the frequency and the pulse width stored in the storage unit is applied to the sound source, and

the pulse signal application unit intermittently applies the pulse signal that alternately occurs at a plus side and a minus side based on a neutral intermediate zero potential at which no current flow.

2. The sounder according to claim 1 , wherein when the frequency of the pulse signal is determined by a predetermined method, the pulse signal application unit obtains a pulse width corresponding to the determined frequency from the storage unit, and generates the pulse signal so that the pulse signal of the determined frequency and the obtained pulse width is applied to the sound source.

3. The sounder according to claim 1 , wherein the pulse signal application unit generates the pulse signal so that the pulse duty ratio of the pulse signal becomes less than 50%.

4. The sounder according to claim 2 , wherein the pulse signal application unit generates the pulse signal so that the pulse duty ratio of the pulse signal becomes less than 50%.

5. A fire detecting system comprising;

an alarm device that detects an abnormality in a monitored region;

a sounder that outputs alarm sound to notify the abnormality in the monitored region; and

a receiving device that is connected to the alarm device and the sounder, wherein,

the alarm device outputs a fire signal to the receiving device when the alarm device detects the abnormality in the monitored region,

the receiving device outputs an alarm sound output signal to the sounder when the receiving device receives the fire signal from the alarm device,

the sounder determines a pitch of alarm sound based on the alarm sound output signal when the sounder receives the alarm sound output signal from the receiving device, and outputs alarm sound of the pitch determined based on the alarm sound output signal, wherein,

the receiving device outputs the alarm sound output signal that contains a control command to control the pitch of alarm sound, and

the sounder determines the pitch of alarm sound based on the control command that is contained in the alarm sound output signal received from the receiving device.

6. The fire detecting system according to claim 5 , wherein,

the sounder comprises a sound source that outputs alarm sound when a pulse signal is applied to the sound source, and a pulse signal application unit that applies the pulse signal to the sound source, wherein

the pulse signal application unit selects a frequency of the pulse signal based on the control command so that the alarm sound is output in the pitch coincided with that of the control command.

7. The fire detecting system according to claim 6 , wherein,

the sounder comprises a storage unit that stores a plurality of combinations of a frequency and a pulse width that the pulse signal can take, wherein

the pulse signal application unit select one of the plurality of combinations stored in the storage unit based on the frequency selected based on the control command, and determines the pulse width of the pulse signal based on the one of the plurality of combinations selected based on the frequency.

8. The fire detecting system according to claim 7 , wherein,

the pulse signal application unit intermittently applies the pulse signal that alternately occurs at a plus side and a minus side based on a neutral intermediate zero potential at which no current flow.