One hertz is one cycle per second, meaning repeating cycle as an event. For example, hertz is applied physics measuring the number of times for a second wave (either acoustic or electromagnetic) is repeated or can be applied, among other uses, to ocean waves that reach the Beach vibrations per second or a solid. The quantity that measures the frequency hertz is called,in this regard, the inverse of the period. One hertz is an oscillation frequency of suffering a particle over a period of one second.

Within the detection systems we can find different types according to their operation, among them the most common:

1. Infrared sensors
2. Vibration sensors.
3. Photoelectric sensors.
4. Ultrasound sensors.
5. Acoustic sensors

Each type of sensor uses different detection methods and each one is recommended according to the situation.

1. Sensors by infraRrojos, are one of the most used types, thanks to its reliable operation and installation, since we can find this type of wired and wireless sensors.
   The infrared sensor has a phototransistor capable of detecting the infrared electromagnetic radiation emitted by a body, this type of radiation is not visible by the human eye. A change of radiation in its perimeter will activate the relay and proceed to send ato alarm signal.
   Within these, there are two models, passive infrared sensor, which only has a phototransistor and assets, which have an emitter and a receiver.
2. Vibration sensors are used mostly in security systems, such as window sensors. car alarms etc.
   Its operation is based on an accelerometer, through a piezoelectric sensor. This type of sensorDue to its construction material it allows to detect changes and pressure when emitting an electric charge.
3. Photoelectric sensors, these are the sensors that use photoelectric rays, normally a transmitter and a receiver are used, they are commonly used in automatic door systems, elevator doors, production chains, etc.
4. The ultrasonic sensors are those that emit an acoustic signalabout 30 kHz, a signal that is not appreciated by humans. This signal or wave propagates through space, walls, objects, doors, etc. once the signal has spread the sensor is activated and any change will trigger the sensor.
   These types of sensors are also used in devices that require measuring distances and detecting objects.
5. Acoustic sensors, are those that can detect the signal emitted by anyobject and are able to detect the pressures that the acoustic waves emit, such as the noise of the crystals when breaking a window.

This type of batteries are very common in devices such as watches, computers, calculators, remote controls etc .. thanks to its small size is ideal for small devices.

Its very peculiar shape is of cylindrical and flat type, with two discs, one upper connected to the positive pole (4) and one in the lower part connected to the negative pole (5).

According to the model we will find them with voltages of vary between 1.2and 3 V (3).

This type of stack can be divided into two large groups:

• Primary batteries: They are depleted as they are used.
• Secondary batteries: They can be recharged by passing an electric current through them in the opposite direction.

Since there are numerous types of button-type batteries in the market, it is advisable that before buying it, the model of the battery is verified, all battery models inu upper part indicate the model, normally this reference begins with two or three letters (1) followed by a numbering (2).

It is mandatory to dispose of exhausted batteries at a recycling point, as these types of batteries are highly polluting due to their composition.

1. Metal cathode (+).
2. Zinc anode (-).
3. Zinc (Electrolytic).
4. Isolation.
5. Separator (porous).
6. PaAg2o sta.

Inside the button cells you will find 4 types according to their chemical composition.

• Alkaline: They are the most common, are composed of zinc as anode and manganese dioxide (MnO2) as cathode, its voltage is 1.5 volts, the most common: LR54, LR44, LR43, LR9.
• Lithium: Its chemical composition can be Manganese-Lithium Dioxide, LiMnO2, Polycarbonate-Lithium Monofluoride or Thionyl Chloride-LiUncle Tadiran. The most common, CR1025, CR1216, CR1220, BR1225, CR1612, CR1616, CR1620, CR1632, CR2016, CR2025, BR/CR2032, BR2325, BR/CR2330, CR2354, CR2450, CR2477, CR3032. Their voltages vary between 3 and 3.6 volts.
• Silver oxide: Very good at low temperatures, its voltage is 1.55 volts. The most common, SR41, SR42, SR43, SR44, SR45, SR48, SR54, SR55, SR57, SR58, SR59, SR60, SR62, SR63, SR64, SR65, SR66, SR67, SR68, SR69.
• Zinc air cells: Normally used in hearing aids, their voltage is 1.4 volts., The most common: PR70, PR48, PR41 or PR44.