Telephony
Telephony (/təˈlɛfəni/ tə-LEF-ə-nee) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties.
If the called station answered, the operator disconnected their headset and completed the station-to-station circuit.
Later, conversion to installation of jacks that terminated the inside wiring permitted simple exchange of telephone sets with telephone plugs and allowed portability of the set to multiple locations in the premises where jacks were installed.
The first implementation of this, ISDN, permitted all data transport from end-to-end speedily over telephone lines.
The integration of telephony software and computer systems is a major development in the evolution of office automation.
Following the development of computer-based electronic switching systems incorporating metal–oxide–semiconductor (MOS) and pulse-code modulation (PCM) technologies, the PSTN gradually evolved towards the digitization of signaling and audio transmissions.
[9][10] MOS technology was initially overlooked by Bell because they did not find it practical for analog telephone applications, before it was commercialized by Fairchild and RCA for digital electronics such as computers.
[11][6] MOS technology eventually became practical for telephone applications with the MOS mixed-signal integrated circuit, which combines analog and digital signal processing on a single chip, developed by former Bell engineer David A. Hodges with Paul R. Gray at UC Berkeley in the early 1970s.
[12] MOS SC circuits led to the development of PCM codec-filter chips in the late 1970s.
[6][5] The silicon-gate CMOS (complementary MOS) PCM codec-filter chip, developed by Hodges and W.C. Black in 1980,[6] has since been the industry standard for digital telephony.
A solution to this issue was linear predictive coding (LPC), a speech coding data compression algorithm that was first proposed by Fumitada Itakura of Nagoya University and Shuzo Saito of Nippon Telegraph and Telephone (NTT) in 1966.
LPC was capable of audio data compression down to 2.4 kbit/s, leading to the first successful real-time conversations over digital networks in the 1970s.
[16] Another audio data compression method, a discrete cosine transform (DCT) algorithm called the modified discrete cosine transform (MDCT), has been widely adopted for speech coding in voice-over-IP (VoIP) applications since the late 1990s.
[18] A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to the Internet to create, transmit, and receive telecommunications sessions over computer networks.
Direct person-to-person communication includes non-verbal cues expressed in facial and other bodily articulation, that cannot be transmitted in traditional voice telephony.
The research examines many different cues, such as the physical context, different facial expressions, body movements, tone of voice, touch and smell.
Although this diminished ability to identify social cues is well known, Wiesenfeld, Raghuram, and Garud point out that there is a value and efficiency to the type of communication for different tasks.
[23] In The Social Construction of Mobile Telephony it is suggested that each phone call and text message is more than an attempt to converse.
[24] Telephones, depending on the person, help attain certain goals like accessing information, keeping in contact with others, sending quick communication, entertainment, etc.
