Further increasing demands fuelled development towards tone networks which are operated by push buttons using the 12-digit keypad we still find on smartphones.
Increased demand made landline networks evolve from hand-operated switchboards to mechanised pulse networks for which the telephone received a dial. Further increasing demands fuelled development towards tone networks which are operated by push buttons using the 12-digit keypad we still find on smartphones. Again driven by increasing demands, networks evolved to digital transmission.