These networks are in fact the first means of communications that ensure voice transmission through special cables.
Overall, a telephony network dedicated for voice transmission is a specialized network – frequency bands, signal fetching, delays in the transmission of this particular signal.
The network must ensure transmission of the voice signal between any two subscribers, or between multiple subscribers while granting a certain quality of the service: signal/noise report, level of
disruptions, delays, connection awaiting time, connection reject probability etc. the subscriber’s terminal ensures fetching of the voice signal, its conversion into an analogic or digital
signal, connection to the access network.
The analogic or digital access network – allows network access and ensures tele-powering and signalling from the subscriber too (it can ensure multiplexing in certain situations).
The local commutation network and the analogic or digital transit network – ensure connectivity between any two or more subscribers.
The analogic or digital transport network between local and transit commutation points ensure transmissions of the data flows between these commutation points and their multiplexing on large bandwidth.
All telephony networks are subject to a number assignment plan that is approved at the national level.