The called VHF is a Very High Frequency band (hence VHF) ranging from 30 Mhz. to 300Mhz.

The VHF is used for sending audio and video signals between a transmitter and a receiver or between a sender and multiple receivers (broadcast).

The minijack 3.5mm is a popular connector used primarily for headphones although its functionality is much more varied.

It consists of a maximum of three connecting parts being the largest so-called mass or negative polarity and two of smaller size and located farther end of the connector, called living or positive that correspond to each channel, such three-part plug can transmit signals in two different channels, also known as stereo signals. It also exists in a mono minijack but version composed of only two parts, a body and a living or positive.

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.

The UHF connector, also called coaxial connector Amphenol is a RF connection design, created at a time when "UHF" referred to the frequencies above 30 MHz. Originally designed to be used as a video connector radar applications, the connector was later used for RF applications. This connector was developed on the basis of a shielded banana plug.

The UHF band that could normally associated with television channels, is a Spanish band in the electromagnetic spectrum, ranging from 300 MHz to 3 GHz. The UHF band can be affected by variables such as humidity, solar wind, or the time of day that will attempt to connect the device. Although as positive could define the UHF frequency band is high, hence its advantages over short distances.Ultra High Frequency (UHF) Cycles per second: 300 MHz to 3 GHz Wavelength: 100 mm 1 m

We can find 3 types of jack connector, monaural TS connector (tip-sleeve), TRS (tip-ring-sleeve) and TRRS stereo plug (tip-ring-ring-sleeve) which is used in most mobile devices, tablets, MP3 etc ...
We can difference these 3 types of connectors according to their diameter:

1. 6.35 mm jack connector or TS.
2. 3.5mm minijack connector or TRS, is the most common, usually used in headphone's output of portable devices.
3. 2.5mm jack connector or TRRS.

It consists of a maximum of three connecting parts being called the largest mass or negative polarity and two smaller size located more towards the end of the connector,
The called positive that correspond to each channel, such three-part plug can transmit signals in two separate channels, also known as stereo signals. There's a mono version, consisting of only two parts, a negative and a positive.

A. Protector
B. Stem
C. Ring
D. Tip
E. Kindred
F. Ring (Signal Right)
G. Tip (Signal Left)

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.