EMZETT.Telephones
Photo: In short: Devices for voice communication over distance — from the classic landline telephone to the smartphone.
In more detail: While classic landline telephones run over the circuit-switched telephone network, modern phone systems and smartphones increasingly use VoIP, where voice is transmitted as data packets over IP networks.
In Depth
From rotary-dial telephone to smartphone
The classic landline telephone is a pure end device for circuit-switched telephony: a microphone converts speech into an analogue electrical signal, which runs over a dedicated copper line to the nearest exchange. Early devices used a rotary dial, which generated current pulses by turning (pulse dialling); later push-button phones instead sent tone combinations (dual-tone multi-frequency, DTMF) — the same principle still used today in phone menus (“press 1 for…”).
With ISDN, transmission became digital, but remained circuit-switched. The real turning point came with VoIP: speech is broken down into small data packets, which run over shared lines like any other network traffic and are reassembled into a continuous audio stream only at the receiver — considerably more efficient (the line is only loaded during actual speech activity), but more sensitive to network problems like packet loss or fluctuating latency (noticeable as dropouts/delay in the conversation).
From a dedicated device to software
An important shift concerns the question of what even counts as a “telephone” any more. Classically, a telephone was a standalone hardware device with exactly one function. Smartphones, by contrast, are general-purpose computers where telephony is just one of many apps — the same hardware runs internet access, camera, messaging and thousands of other applications in parallel. In business environments, the softphone is increasingly taking over: a pure software application on a PC or smartphone that gets by entirely without a dedicated phone device, using a headset or built-in microphone/speaker instead.
DECT and cordless landline phones
Between the classic corded telephone and the smartphone sit cordless landline phones based on the DECT standard (Digital Enhanced Cordless Telecommunications): a base station is connected by cable to the phone line or a VoIP connection, and the actual handset communicates wirelessly with this base over a short range (typically 20-50 metres, depending on the building). DECT uses its own frequency band (1880-1900 MHz in Europe), which doesn’t collide with Wi-Fi, making DECT connections more robust against interference than Wi-Fi-based solutions.
Compatibility and switching over
When switching from classic to IP telephony, the question often arises of whether existing phone hardware can still be used. Many classic desk phones now support SIP directly (SIP phones) and can be connected directly to a VoIP phone system; purely analogue legacy devices need an ATA adapter (Analog Telephone Adapter), which translates between the analogue phone and the IP network.
See also: Telephony, Smartphones