Relay

Relay is an electrical control device. It has a control system (also known as the input circuit) and the control system (also known as the output circuit) the interaction between. Often used in automatic control circuit, it is actually with a small current to control high current operation of an "automatic switch." It plays in the circuit automatically adjust security, conversion circuitry and so on. Working principle and characteristics Introduction
When the input (such as voltage, current, temperature, etc.) reach the required value, the relay output circuits to be controlled is turned on or off. Inputs can be divided into electrical quantities (such as current, voltage, frequency, power, etc.) and non-electrical quantities (such as temperature, pressure, speed, etc.) into two categories. Relay with the fast, stable and long life, small size and so on. Widely used in power protection, automation, movement, remote control, measurement and communications devices. Electromagnetic relay works and features Relay Products (19) are generally electromagnetic relay core, coil, armature, composed of reed contacts. As long as both ends of the coil with a certain voltage, coil current will flow through certain to produce electromagnetic effects, the armature will be attracted to the role of the electromagnetic force to overcome the spring tension to return to the core absorption, so as to drive the armature dynamic contact with the stationary contact (normally open contact) pull. When the coil power, the electromagnetic suction disappeared, the armature reaction in the spring will return to the original position, so that the static dynamic contact with the original contact (NC contact) release. This pull-release, so as to achieve the conduction in the circuit, cutting off the goal. For the relay "normally open, normally closed" contact, it can be to distinguish: the relay coil is not energized in a disconnected state when the static contact, known as the "normally open contact"; in a static on-state contact point known as the "normally closed contacts." Generally has two relay circuit for low voltage control circuits and high-pressure work circuit. Solid State Relay (SSR) of the working principle and characteristics of Solid State Relay [1] is a two terminal for the input, the other two terminals for the output of the four-terminal devices, the use of isolation among input and output devices to achieve electrical isolation. Solid state relays by the type of load power AC-and DC can be divided into type. The switch type can be divided normally open and normally closed type. Isolation can be divided according to type of hybrid, transformer isolated and optically-isolated, with optical isolation for the most. Thermal reed relay works and features Thermal reed relay is a magnetic material using thermal detection and temperature control of the new thermal switch. It consists of thermal magnetic, permanent magnetic ring, reed, thermal installation piece, plastic substrates and other accessories. Thermal Reed Relays do not coil excitation, generated by the permanent magnetic ring magnetic drive switching. Permanent magnetic ring can provide to the magnetic reed switch from the thermostat temperature magnetic characteristics of the decision. Reed Relay Reed relay is a coil generates a magnetic field to control actuation of the reed relay, the coil as a sensing device. Therefore, the reed relay features, small size, light weight, fast response, short beating time characteristics. When the entire ferromagnetic metal or other magnetic material with close to a time when the action open or closed circuit. By the permanent magnets and reed tube. Permanent magnet, the reed switch is not fixed in a non-magnetic with a magnetic stand. A permanent magnet poles of the connection as the axis, this axis should the axis of reed or coincidence coincident. From far and near permanent magnet and the adjustment of the distance between the reed switch, reed switch occurred just when the action (for normally open reed, into closed; for normally closed reed switch, becomes disconnected) when the position of the magnet fixed. At this time, when entire magnetic materials, such as iron and close to the magnet and the reed, the reed will happen again moves back to the state when no magnetic field; when the iron leaves, reed the action occurs in the opposite direction. Reed relays, solid structure, contact is sealed, high durability, the location of mechanical equipment can be used as limit switches, can also be used to detect iron doors and windows are in the specified location. Light Relay Optical relay for the AC / DC and used in the semiconductor relay, light-emitting devices and integrated optical devices by device. Input side and output side of the electrical insulation, but the signal can be transmitted through the optical signal. Characterized as semi-permanent life, small current driving signal, high impedance insulation, ultra-small, light transmission, no contact ... and so on. Mainly used in test and measurement equipment, communications equipment, security equipment, medical equipment ... and so on.

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Relay

Basic information

Relay is a transmission channel between two points, both of which are usually exchange center. Trunks are carrying multiple logical link of a physical connection. Along with the science and technology development, relay concept is not only applied in wireless communication, network communication switch trunk can also call a relay.

principle

The basic principle of relief theory is at the end of the 19th century mathematicians Erlang proposed, Danish study how he devoted himself to the limited service capacity for a lot of customer service. Now, use his name as traffic intensity of the unit. A Erlang said a fully occupied in a channel traffic intensity (i.e. unit hours or unit minutes of call duration). For example, a in one hour occupied a 30-minute channel traffic for 0.5 Erlang.

Wireless communications, relay concept refers to allow large number of users in a village in relatively small number of Shared channel, namely from available channel repository to give each user on-demand channel.

In relay wireless systems, each user just in a call when it allocate a channel, once call terminated, originally occupied by the channel immediately return to available channel repository.

According to user behaviour statistics, relay make fixed number of channels or lines can be a quantity greater, random user community service. Telephone company according to relay theory to decide which has hundreds of thousands sets telephone office building of the number needed distribution circuit. Relay theory is also used in cellular wireless systems design, in the available telephone lines in a contact number and peak no lines are available between the possibility of a compromise. When the telephone lines declined, for a specific user, all line busy all the possibility of bigger. In relay of the mobile wireless systems, when all wireless channels are occupied and users and, when they occur to request service call obstruction or system refuse access. In some systems, may use queuing ways to keep is asking conversation user information, until one channel so far.

Basic term definition

Relay theory used in basic terms definition:

Build time:

Give the user is asking to allocate a relay radio channel of time required

Obstruction call:

Because of congestion cannot finish in the request of the call, also called loss call

Keep time:

A typical call the average time to maintain, expressed as H (in seconds for the unit)

Traffic intensity:

Characterization channel availability, efficiency, and the average occupancy rate for channel to Erlang for the unit. It is a dimensionless value, usable to represent the single or multiple channel availability. Expressed as A

Load:

The whole system of traffic strength to Erlang for the unit

Service level (GOS) :

The amount of characterization congestion level, defined as a call blocking probability (expressed as B, the unit is Erlang), or delay time more than one particular time of the probability (expressed as C, the unit is Erlang)

Request rate:

Unit time average call requested times. Expressed as l/SEC

The stock of the rise in relief

Banker in pull litre share price, discover cast dish is overweight, to cleanse them from these float to prepare, need a wash dish finishing process, in K line represents a box-like finishing shape, in share price on expression is fluctuate and we put the finishing form called up relay form.