How does modern telephony work ?
The telephone in your home/office converts your speech into an analogue electrical signal which travels along the copper wires to the telephone exchange. The telephone exchange ‘samples’ your conversation (measures the electrical signal from your phone many times per second, and records a series of equivalent digital measurements) and groups these numbers into ‘packets’ representing, say, 1/10th second of conversation. Your telephone exchange takes the packets of 20 different conversations and sends them one after another down the wire to another exchange, which separates the packets into separate conversations and converts them back to analogue signals for playing to the party you are talking with. Because electrical signals travel fast, all of this can happen without you noticing any delay. Telcos have been building and refining this technology and building their infrastructure for decades – the digital exchanges just described have been digitising and multiplexing your phone calls s
