Type of signal
1. Pre warning: 36 sec blast, pause followed by another 24 sec blast, pause and this sequence
will repeat for 3 min.
2. Red alert: 6 sec blast, pause followed by another 6sec blast, pause and this sequence
will repeat for 3 min.
3. All clear: alarm last 3 min
4. Disaster warning: 15 sec blast, pause followed by another 15 sec blast, pause and this
sequence will repeat for 3 min.
5. Free warning: hand control