Modern telephone circuitry
| Added: 15-03-2009 Author: J.C. Banks Category: Phone Systems |
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Telephone level electrical tests in decibels. Decibel has no numeric value, but only used to describe the ratio between two voltages, currents, power, or impedance. Using the logarithmic decibel called primary LOG 10. To calculate revenue, the current SPL, range: 20 Log X1/X2. To calculate the power = 10 log P1/P2.
A two-round hard wire phone connects major service providers referred to as telco. The choir is known as tip and ring wires. -48 Volts DC Hubeba tip and ring on the ground potential. Tip and ring conditions previously known part of the operator of each connector is plugged into the bank to manually switch. General twisted pairs of wires to measure the value that is 22 Ludwig Hertz 300-3,000 address but actually work at higher frequencies.
Telephone circuit is the basic assumption that the impedance 600 ohms. In fact, impedance depends on frequency, impedance value varies with the signal. The ltered lines attenuates the 300 Hz signal of about 4 dB per 12,000 feet. At 5 kHz, the attenuation jumped up to 14 dB per 12,000 feet. This attenuation distortion can cause problems, especially for digital signals.
Small attenuation and distortion of the Federal Communications Commission. The FCC has explained attenuation distortion as the difference in profits in connection with a memory frequency of 1004 Hz tone. To overcome the problem of signal attenuation in the frequency, inductance added phone lines. Time-line for this practice involves. New bears are marked H, D or B to indicate the added inductance of each 6.000, or 3000 ft 4500 Standard is the addition of the added inductance 44, 88 or 135 mh which is also printed on the line.
Delay distortion is another problem resulting from the traditional character of 2 pairs of wire. The FCC also set a limit of delay distortion. Value of the main phone line can not exceed 1.750 microseconds between 800 and 2600 Hz. Special LC filter can be called a late late equalizer will be used to reduce distortion. Telcos are also to be aware of C2 lines designated as lines that provide high levels of attenuation and delay distortion.
Attenuation distortion, delay distortion, bandwidth limit the physical size and all have a pair of copper wires that caused many of the world upgrade telephone systems, fiber optic cable.
Phone system that uses a variety of programs gnaling me. Common types used is Pulse, DC to DC Voltage Polarity, Multi-Frequency and Inter I gnaling-Common Channel Signaling Office. Nadi gnaling uncommon in step by step and crossbar systems. This is used to represent the number dialed, either directly or through a Pulse is sent from the central office switch, switch destination. Although not common today, is still used in rare cases.
Voltage polarity changes, and changes (such as beans) are used in some inter-office and I gnaling panel routine. This method is still used today specifically telco leased line that connects the radio transmitter to control the distance protection. DC phone reception took control and AC signals that send and receive audio intelligence.
Multi-frequency or MF I gnaling used between offices and toll tandem systems. Dual frequency used to send tons of information the phone number to call in the network. Ton is in the 300Hz to 3000Hz band telecommunications systems are usually sound. Many MF toll trunks for use in the United States and Canada as a 2600 Hz line management and lazy. Some areas are used 3.750 Hz (outside the band) to regulate / control the unemployment line. MF gnaling I sometimes referred to as the R1 I gnaling. R2 is an international bi-directional version of my MF gnaling used throughout the world. MF I gnaling relatively slow and vulnerable to fraud victims.
Common Channel Inter-Office Signaling is used to send information between tandems and network switches. CCIS works by sending information from 300Hz to 3000Hz band along the circle of voice and data circuits. CCIS faster and more susceptible to fraud than I gnaling toll MF. Modern CCIS program called Signaling System 7. SS7 is used in the United States, Canada, UK, Australia and most of the world.
Various techniques are used to transmit phone service with Open Wire Carrier, Coax Cable, microwave and fiber optic systems Tower.
Open wire carrier, they carry several calls over copper wire pairs simultaneously using frequency division multiplexing (FDM). About100Khz frequency bands and 4 kHz channel space. Open wire carrier used in the United States halted several years ago.
Coaxial cable transmission is used with the same clear and as the bearer wire. Coaxial cable is open cable carrier. Application in urban areas during the open wire carrier used in the rural environment. Frequency division multiplexing is used for coaxial cable transmission. Today's coax cable telephone transmission is limited in some areas, especially if the system administrator.
In the 1950s, microwave transmission becomes widespread transmission between the phone. Microwave frequency division multiplexing. Microwave is still widely used U.S. and internationally. The system is still in service are often a good backup or a system will be used as part of a digital transmission techniques.
Modern systems include a phone transmissions eye clean glass fibers using amplitude modulated infrared light, which is known as fiber optics. Revolutionizing the way communication transmission methods. Fiber optics provide high bandwidth transmission and Again, and their wide applications in North America and most of the industrialized world.
Almost every aspect of telephone service includes research and innovation. When the phone system changes have been beautiful in the last century, the future benefits can revolutionize our ideas inferior. For this change will directly result of research conducted in the electronic, computer and mechanical.
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