This fourth circuit is designed to produce the typical wailing sound commonly heard in police sirens. The IC 555 can be also used for making a perfectly imitating police siren circuit as demonstrated above. This causes the speaker to generate the required sharp high volume warble alarm sound at 1 Hz rate. The 1 Hz alternate high low supply at pin 5 of IC2 forces the output pin #3 voltage of IC 1 to generate a symmetrically changing frequency varying from 500 Hz to 440 Hz. We know that pin 5 can be used with an external high/low signal for modulating the pin 3 output with a corresponding widening/narrowing pulse widths. Also known as he-haw alarm, these are commonly used in European emergency vehicles. If you want to convert the previous design into an ear piercing warble alarm, you can do it by simply replacing the D1 diode with a 10 K resistor as revealed in the above diagram. This produces a 1Hz sharp pulsed alarm effect on the loudspeaker. This in turn causes pin 3 800 Hz pulse width to narrow to an extent which almost turns OFF Q1. Here IC 2 is configured as a 1 Hz oscillator circuit which causes pin 5 of IC 1 to alternately become low at a 1 Hz rate. We have already studied how pin 5 can be used for controlling the pulse width of the IC 555.
Red alert alarm generator#
The previous 800 Hz monotone alarm could be converted into a more interesting pulsed 800 Hz alarm by adding another astable multivibrator with the tone generator circuit as shown in the second concept below. Since the design may produce a high level of ripple voltage, D1 and C3 are included to prevent the ripple interference with the IC 555 functioning.ĭiodes D2 and D3 are included to neutralize the inductive switching spikes generated from the speaker coil, and to safeguard the transistor Q1 against damage.
Red alert alarm driver#
A safe value could be around 70 Ohms 1 watt.įor making a high power continuous tone alarm circuit we cam upgrade the above circuit through a power transistor driver Q1 and a more powerful loudspeaker, as shown below:
Red alert alarm windows#
Installed at call points next to each bed or within an area, Nurse Call can be integrated with a telecare system to enable the person to control a range of environmental devices such as opening and closing doors, windows or curtains or turning on lights, televisions or digital boxes.The speaker can have any impedance value, due to the presence of the current limiting resistance Rx. In the care sectorįor hospices, hospitals and residential homes, Nurse Call systems are an easy way for residents and patients to summon assistance. This simple system provides peace of mind to relatives and carers as well as giving individuals the reassurance that help is close at hand if they need it. Most people prefer to live independently in their homes for as long as they can safely do so. The alarm system can also be enhanced to include a range of sensors which remotely trigger an alarm for situations including smoke, carbon monoxide, floods, a seizure or a fall.
By pushing a wireless pendant or hardwired button they can instantly notify a call centre, warden or relative that help is needed. In the homeĪ telecare system is the latest technology that allows people living in their own home to quickly and easily raise the alarm should they find themselves in difficulty.
So whether they are living in their own home, a residential setting or a hospital – they can still enjoy a level of freedom that they otherwise would not have. Red Alert offers a range of telecare products designed to offer vulnerable people a level of safety, independence, dignity and control over their day-to-day lives.
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