VoIP and PLC, analog and digital paging intercom system

With the development of the industrial Internet, VoIP paging intercom system are increasingly used in paging and intercom communication applications in the industrial field.  So what is a VoIP paging intercom system? Compared to analog system, digital system, and PLC system, what is the benefits of VoIP system?
Today, let’s talk about what a VoIP system is, how it differs from other type of systems, and what is the advantages.

VoIP system, Voice over Internet Protocol, abbreviated as VoIP, it is a voice transmission phone based on IP networks.
The basic principle of VoIP is to compress the voice data encoding through the voice compression algorithm, and then package the voice data according to the TCP/IP standard, send the data packets to the receiving place through the IP network, and then string the voice data packets. After decompression processing, the original voice signal is restored, thereby achieving the purpose of transmitting voice by the Internet.

VoIP adoption method:
IP telephone interconnected with the public telephone network: make voice transmission through broadband or dedicated IP network. The terminal could be a PC or a dedicated IP phone.

VCommon protocols for VoIP communication:
H.323, SIP, MEGACO, MGCP, etc.
H.323 is one of a set of standards from the ITU-T, this standard includes point-to-point and multi-point conferences.
MGCP, the Media Gateway Control Protocol, is a control protocol that allows the central console to monitor IP phone and gateway events and notify them to send content to the specified address.
MEGACO, Media Gateway Control Protocol, Megaco/H.248 is a protocol for controlling the protocol units of a physically separate multimedia gateway, so that call control can be separated from media conversion.

Advantages of VoIP
● No computer required.
● Guarantee long-term online.
●Clear sound quality.
● Effectively solve the problems of echo cancellation, data packet loss and network jitter.
● Easy to change number and display numbers.
● Can connect to wireless network equipment.。
● No distance limit, can talk everywhere of the world through IP.
● Good expandability, can configure with more than 2000 telephones.
● Encrypted communication.
●Support multiple communication interfaces, single-mode fiber, multi-mode fiber, network cable.
● Versatility, can carry out voice call, call recording, paging, intercom and central control scheduling functions.

Let’s focus on its communication interface, optical fiber and network cable:

Optical fiber
The reason why optical fiber communication has received great attention is that it has unparalleled advantages compared with other communication methods.

Advantage:

● Large communication capacity.
In theory, an optical fiber with only the thickness of hair can transmit 100 billion voice channels simultaneously. It is dozens or even thousands of times higher than traditional open wire, coaxial cable, microwave, etc. The transmission capacity of an optical fiber is so large, and an optical cable can include dozens or even thousands of optical fibers. If wavelength division multiplexing technology is added to use an optical fiber as several or dozens of optical fibers, its The communication capacity is even more amazing.
● Long relay distance.
Due to the extremely low attenuation coefficient of optical fiber, if equipped with appropriate optical transmission and reception equipment, the relay distance can be more than several hundred kilometers. This is unmatched by traditional cables (1.5km), microwaves (50km), etc. Therefore, it is entirely possible to realize global non-relay optical fiber communication in the near future.
● Good security performance, light waves are only transmitted in the core area when they are transmitted in the optical fiber, and basically no light "leaks" out.
● Small size and light weight, easy for construction and maintenance.
● The laying method of the optical cable is convenient and flexible.
● The potential cost is low, the raw material is sand, the source is abundant and the price is low.
● Low maintenance cost, optical fiber can run stably for 5-10 years without maintenance.
Disadvantage：
● Optical fiber requires professional equipment. The fusion splicer is between several thousand and ten thousand yuan. The installer needs to have certain professional knowledge.
●  Optical fiber requires optical equipment at both ends, and the cost is higher.
Network cable:
Advantage：
● Easy for installation, not high requirements for the installation personnel.
● The wiring is feasible and can be wired at right angles.
● Construction and maintenance are more convenient.
Disadvantage:
● The transmission distance is short, it is 100 meters in theory, and the project is generally 80-90 meters.
● Electric signal transmission is susceptible to electromagnetic interference.
● Easy to damage and high maintenance cost.

Power Line Carrier communication-PLC, refers to a special communication method that uses high voltage power line, medium voltage power line or low voltage distribution line as an information transmission medium for voice or data transmission.
Power line carrier communication (PLC) is a communication method popularized earlier by the power system. The main feature is the use of power lines to transmit modulated signals. It can be networked without re-establishing network cables, and is welcomed by some users.
● With the advancement of broadband (frequency) carrier solutions in recent years, the application surface of power line carriers has been gradually compressed. Ultimately, it is caused by several shortcomings of power line carrier communication itself.
● The pulse interference existing in the power line itself. The AC frequency of the State Grid is 50Hz, and the period is 20ms and 16.7ms. In each AC cycle, there will be 2 peaks and 2 pulse interferences at the same time, that is, the inherent 100Hz/120Hz pulse interference on the power line, the interference time 2ms.
● The power line causes a reduction in the carrier signal. When the power line is empty, data can be transmitted for several kilometers. When the load on the power line increases, the channel that the carrier signal can be used for communication is quickly reduced, causing delays, packet loss, and other failures.。
● The blocking effect of the distribution transformer. The physical circuit block will directly cut off the network data communication, and the power line carrier is limited to use in a complete line.
With the development of other communication methods in the field of communication, the power line carrier technology has gradually declined. Apart from the application in the remote meter reading system, there is no other use.

Analog communication adopts sine wave amplitude, frequency or phase changes, or pulse amplitude, width or position changes to simulate the original signal to achieve the communication, so it is called analog communication.
Advantage：
● The equipment of analog communication system is simple and the occupied frequency band is narrow.
● Cheap price.
Disadvantage:
● Poor confidentiality. It is easy to be eavesdropped, as long as the analog signal is received, the communication content can be easily obtained.
● Weak anti-interference ability. The electrical signal will be interfered by various noises from the outside and the communication system during the transmission along the line. It is difficult to separate the noise and the signal after mixing, thereby deteriorating the communication quality.
● The shorter the transmission distance, the longer the line, the more noise accumulation.
● Because of the limitation of the power provided by the host, it does not have the broadcast function.

Digital communication is a communication method that uses a digital signal as a carrier to transmit a message, or uses a digital signal to digitally modulate a carrier wave and then transmits it. It can transmit digital signals such as telegraph and digital data, as well as analog signals such as speech and images that have been digitized.
Advantage：
● Strengthen the confidentiality of communications. After the A/D conversion, the voice signal can be encrypted first and then transmitted. After decryption at the receiving end, it can be restored to an analog signal by D/A conversion.
● Improve the anti-interference ability, especially in the relay, the digital signal can be regenerated to eliminate the accumulation of noise.
● Transmission errors can be controlled, thereby improving transmission quality.
● It is convenient to use modern digital signal processing technology to process digital information.
● An integrated digital communication network can be constructed to deliver various messages in a comprehensive manner, which enhances the functions of the communication system.
Disadvantage:
● The frequency band utilization rate is not high.
● The technical requirements are complex, and the quantization error will be caused during the analog-to-digital conversion.
● Requires strict synchronization system (carrier synchronization, bit synchronization, group synchronization, network synchronization).
In summary, VoIP industrial paging intercom system are more suitable for the application of industries such as ports, ships, power plants, steel plants, railway, tunnels, pipe corridors, etc., especially in places with interference and harsh environments. At the same time, it is more suitable for the application of further automation.