Telephone Wikipedia. For the handheld personal computer, see Smartphone. Modern telephones use push buttons. A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. In 1. 87. 6, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice. This instrument was further developed by many others. The telephone was the first device in history that enabled people to talk directly with each other across large distances. Telephones rapidly became indispensable to businesses, government, and households, and are today some of the most widely used small appliances. The essential elements of a telephone are a microphone transmitter to speak into and an earphone receiver which reproduces the voice in a distant location. In addition, most telephones contain a ringer which produces a sound to announce an incoming telephone call, and a dial or keypad used to enter a telephone number when initiating a call to another telephone. Until approximately the 1. DTMF push button dial, first introduced to the public by AT T in 1. View and Download Verizon FiOS TV user manual online. Verizon FiOS TV User Guide. FiOS TV TV pdf manual download. View and Download Pioneer VSX832 instruction manual online. VSX832 Receiver pdf manual download. Cenvat Credit of InputsInput ServicesCapital Goods Landmark Service Tax Judgments Cenvat Credit. What is Cenvat Credit. Cenvat Credit Scheme provides for. PREVIEWS/32547224/23432455/egyeb/prima_lc-15ys031.pdf_1.png' alt='Prima Tv Service Manual' title='Prima Tv Service Manual' />The receiver and transmitter are usually built into a handset which is held up to the ear and mouth during conversation. The dial may be located either on the handset, or on a base unit to which the handset is connected. The transmitter converts the sound waves to electrical signals which are sent through a telephone network to the receiving telephone which converts the signals into audible sound in the receiver, or sometimes a loudspeaker. Telephones are duplex devices, meaning they permit transmission in both directions simultaneously. The first telephones were directly connected to each other from one customers office or residence to another customers location. Being impractical beyond just a few customers, these systems were quickly replaced by manually operated centrally located switchboards. This gave rise to landline telephone service in which each telephone is connected by a pair of dedicated wires to a local central office switching system, which developed into fully automated systems starting in the early 1. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the middle 2. Hand held mobile phones were introduced for personal service starting in 1. By the late 1. 97. Plasma_FHD_Repair.jpg' alt='Prima Tv Service Manual' title='Prima Tv Service Manual' />In 1. Advanced Mobile Phone System AMPS was launched, offering a standardized technology providing portability for users far beyond the personal residence or office. These analog cellular system evolved into digital networks with better security, greater capacity, better regional coverage, and lower cost. Today, the worldwide public switched telephone network, with its hierarchical system of many switching centers, can connect any telephone on the network with any other. With the standardized international numbering system, E. Although originally designed for simple voice communications, convergence has enabled most modern cell phones to have many additional capabilities. They may be able to record spoken messages, send and receive text messages, take and display photographs or video, play music or games, surf the Internet, do road navigation or immerse the user in virtual reality. Since 1. 99. 9, the trend for mobile phones is smartphones that integrate all mobile communication and computing needs. Basic principles. A traditional landline telephone system, also known as plain old telephone service POTS, commonly carries both control and audio signals on the same twisted pair C in diagram of insulated wires, the telephone line. The control and signaling equipment consists of three components, the ringer, the hookswitch, and a dial. Prima Tv Service Manual' title='Prima Tv Service Manual' />The ringer, or beeper, light or other device A7, alerts the user to incoming calls. The hookswitch signals to the central office that the user has picked up the handset to either answer a call or initiate a call. A dial, if present, is used by the subscriber to transmit a telephone number to the central office when initiating a call. Until the 1. 96. 0s dials used almost exclusively the rotary technology, which was replaced by dual tone multi frequency signaling DTMF with pushbutton telephones A4. On Nodevice you can download service manuals, repair manuals, schematics in PDF, DJVU to repair, recover, restore, fix your device. A major expense of wire line telephone service is the outside wire plant. Telephones transmit both the incoming and outgoing speech signals on a single pair of wires. A twisted pair line rejects electromagnetic interference EMI and crosstalk better than a single wire or an untwisted pair. The strong outgoing speech signal from the microphone transmitter does not overpower the weaker incoming speaker receiver signal with sidetone because a hybrid coil A3 and other components compensate the imbalance. The junction box B arrests lightning B2 and adjusts the lines resistance B1 to maximize the signal power for the line length. Telephones have similar adjustments for inside line lengths A8. What City Is Zip Code 78214 on this page. The line voltages are negative compared to earth, to reduce galvanic corrosion. Negative voltage attracts positive metal ions toward the wires. Details of operation. PREVIEWS/32547224/23432455/prima/prima_lc20y15_lcd_tv_sm_only_chi.pdf_1.png' alt='Prima Tv Service Manual' title='Prima Tv Service Manual' />The landline telephone contains a switchhook A4 and an alerting device, usually a ringer A7, that remains connected to the phone line whenever the phone is on hook i. A4 is open, and other components which are connected when the phone is off hook. The off hook components include a transmitter microphone, A2, a receiver speaker, A1, and other circuits for dialing, filtering A3, and amplification. A calling party wishing to speak to another party will pick up the telephones handset, thereby operating a lever which closes the switchhook A4, which powers the telephone by connecting the transmitter microphone, receiver speaker, and related audio components to the line. The off hook circuitry has a low resistance less than 3. DC, which comes down the line C from the telephone exchange. The exchange detects this current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern push button telephone, the caller then presses the number keys to send the telephone number of the called party. The keys control a tone generator circuit not shown that makes DTMF tones that the exchange receives. A rotary dial telephone uses pulse dialing, sending electrical pulses, that the exchange can count to get the telephone number as of 2. If the called partys line is available, the exchange sends an intermittent ringing signal about 7. AC in North America and UK and 6. Germany to alert the called party to an incoming call. If the called partys line is in use, the exchange returns a busy signal to the calling party. However, if the called partys line is in use but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call. The ringer of a telephone A7 is connected to the line through a capacitor A6, which blocks direct current but passes the alternating current of the ringing signal.