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.

Secure Digital (SD) is a memory card format for portable devices such as digital cameras, mobile phones, laptops and even game consoles (both desktop and laptop), among many others.

SDHC Speed Class 2 Class 2 2 MB/s
SDHC Speed Class 4 Class 4 4 MB/s
SDHC Speed Class 6 Class 6 6 MB/s
SDHC Speed Class 10 Class 10 10 MB/s
UHS Class 1 UHS Class 1 10 MB/s
UHS Class 3 UHS Class 3 30 MB/s

hen we talk about IP code (International Protection) we talk about an international standard (IEC 60529) which classifies the protection against external factors, solid or liquid, that has a component or electronic device; LED strips, controllers, meters, security cameras, etc.

This alpha-numerically standard has been designed to sort different levels of protection. Nomenclature starts with IP followed by two numeric values.

- Example IP68:

The first value ranges from 0 to 6 and indicates the protection against solid agents. In this case, strong protection against dust.

The second value is between 0 and 8 and indicates the protection against liquid agents. In this case the complete and prolonged immersion during the time specified by the manufacturer.

We could say that the larger the number is greater IP protection has a device.

In below table, we can see different IP protections levels available.

IPXX	First digit (IPxx)	Second digit (IPxx)
0	Unprotected.	Unprotected.
1	Protection against objects of> 50 mm diameter.	Protection against vertically dripping water.
2	Protection against objects of> 12.5 mm diameter.	Protection against inclined drip water up to 15°.
3	Protection against objects of> 2 mm in diameter.	Protection against water projected from any direction, up to 60°.
4	Protection against objects of> 1 mm in diameter.	Protection against splashing water any direction.
5	Ingress of dust is not entirely revented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment .	Protection against water jets.
6	Dust tight.	Protection against strong jets of water.
7		Protection against complete immersion up to 1 meter for 30 minutes.
8		Protection against complete and prolonged immersion.

The Wifi technology is a wireless communication mechanism between devices. This technology allows you to connect devices such as computers, laptops, mobile etc... to the Internet or communicate with the devices themselves.

Applications can be several, among the most common are the access points, ideal for giving and sharing a connection signal to multiple devices. It is the typical configuration of a home user.
Repeater, ideal to repeat and amplify weak signal.

The power and range between devices basically depends on the antenna and its hardware.

The wireless signals work under a unified standard regulations, the standard that is based on the IEEE 802.11. These include IEEE 802.11b, IEEE 802.11g and IEEE 802.11n working at 11 Mbit/s, 54 Mbit/s and 300 Mbit/s, respectively.
Being any device with a standardized protocol such technology can connect to another using the same technology, making it a kind of universal connection.

The wireless networks are characterized by the ease and convenience of making connections in infrastructure, since it is not necessary to perform network cable installations.
it also allows connecting a lot of devices to a single node.

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.