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Telephone

1. Telephone Invention History: – Term ‘telephone’ used for various inventions before electric telephone – Johann Sigismund Gottfried Huth’s telephon in 1796 – Captain John […]

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1. Telephone Invention History:
– Term ‘telephone’ used for various inventions before electric telephone
– Johann Sigismund Gottfried Huth’s telephon in 1796
– Captain John Taylor’s telephone for sailing vessels in 1844
– Johann Philipp Reis’ Reis telephone in c.1860
– Dispute over invention credit among inventors like Bell, Meucci, Reis, Gray
– Bell awarded first US patent for electric telephone in 1876
– Bell’s patent improved on existing voice transmission methods
– Bell’s patent became basis for other telephone patents
– Hungarian engineer Tivadar Puskás proposed telephone switch in 1876

2. Telephone Components and Evolution:
– Essential elements: microphone (transmitter) and earphone (receiver)
– Handset combines receiver and transmitter for conversation
– Transmitter converts sound waves to electrical signals
– Receiver reproduces sound from incoming signals
– Alerting features like ringers or visual indicators for incoming calls
– Early telephones directly connected between customers
– Manual switchboards replaced direct connections
– Worldwide public switched telephone network (PSTN) formed
– Mobile radio systems developed for mobility
– Introduction of handheld mobile phones for personal service starting in 1973

3. Telephone Technology Advancements:
– Introduction of transistor in 1947 revolutionized telephone technology
– Stored program control and MOS integrated circuits improved switching systems
– Introduction of pulse-code modulation (PCM) led to digital telephony
– Integrated Services Digital Network (ISDN) launched in the 1980s
– Internet Protocol (IP) telephony (VoIP) rapidly replacing traditional networks
– VoIP market valued at $85.2 billion in October 2021
– VoIP market projected to reach $102.5 billion by 2026
– Internet-based digital service requires special provisions for emergency services

4. Mobile Phones and Smartphones:
– Analog cellular networks appeared in 1979, digital networks in early 1990s
– Mobile phones incorporate LCD or OLED displays
– Smartphones combine mobile phone and personal computing device functionalities
– Smartphones operate primarily via graphical user interface and touch screen
– Smartphones offer internet access through cellular networks and Wi-Fi
– Popular mobile phone operating systems include Android and iOS

5. Satellite Phones Overview:
– Satellite phones connect via satellites orbiting Earth
– They work in remote areas without cellular service
– Satellite phones provide voice calling, text messaging, and low-bandwidth internet
– They are reliable in emergency situations or natural disasters
– Satellite phones can function where terrestrial networks are unavailable
– Satellite phones are used in hunting, fishing, and mining in remote areas

Telephone (Wikipedia)

A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily 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. The term is derived from Greek: τῆλε (tēle, far) and φωνή (phōnē, voice), together meaning distant voice. A common short form of the term is phone, which came into use early in the telephone's history. Nowadays, phones are almost always in the form of smartphones or mobile phones, due to technological convergence.

AT&T push button telephone made by Western Electric, model 2500 DMG black, 1980

In 1876, 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 at a second device. This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice at a distant location. The receiver and transmitter are usually built into a handset which is held up to the ear and mouth during conversation. The transmitter converts the sound waves to electrical signals which are sent through the telecommunication system to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker. Telephones permit transmission in both directions simultaneously.

Most telephones also contain an alerting feature, such as a ringer or a visual indicator, to announce an incoming telephone call. Telephone calls are initiated most commonly with a keypad or dial, affixed to the telephone, to enter a telephone number, which is the address of the call recipient's telephone in the telecommunication system, but other methods existed in the early history of the telephone.

The first telephones were directly connected to each other from one customer's office or residence to another customer's location. Being impractical beyond just a few customers, these systems were quickly replaced by manually operated centrally located switchboards. These exchanges were soon connected together, eventually forming an automated, worldwide public switched telephone network (PSTN). For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973. In later decades, their analog cellular system evolved into digital networks with greater capability and lower cost.

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