Telephony

The telephone (from the Greek τηλεφωνία of τηλε, AltGr. Pronunciation tele, "far", " far " and φωνή, AltGr. Pronunciation phoné, "voice" ) refers primarily voice communication through a technical device (eg, telephone network). The first researchers who succeeded in this form of transmission of voice data in 1860, was Philipp Reis.

A voice transmission is achieved either by analog or digital telephone services, for example a telephone network (such as ISDN), a radio network ( for example GSM ), or a packet switched data network (for example, IP telephony ). Important is a slight delay and a good sound quality ( up to 200 ms are acceptable ) (most of the speech intelligibility is transmitted because of the frequency range between 300 and 3400 Hz ).

Devices with a wired telephone network phones, in a wireless radio network mobile phones and IP telephony a special IP phone (VoIP or SIP phone) or a computer. For the automatic call answering answering machine or voice mailboxes exist. In radio services radios are used.

When communicating over a telephone network, the goal is addressed via a numerical number, where IP telephony using the IP address, a user name or an ENUM number.