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It’s quite fun to compare today’s technology with what was around when I was a kid. One gadget that always brings a smile to my face is the cordless phone, a device which most of us have in our houses, yet never think twice about. Remember the days when households had a single phone, usually in the hallway, possibly with a longish cord so you could move around a bit? Oh, how times have changed.
Cordless phones exist thanks to a technology called DECT which stands for Digital Enhanced Cordless Telecommunications. DECT systems normally consist of some base or gateway connected to the telephone system and a number of cordless units (for example Panasonic DECT phones for home allow up to 6 handsets) which talk to the base station over radio, microwave to be specific. As with all radio-emitting equipment there has been the usual scaremongering about health affects of radiation exposure, but it’s quite nice to know that there’s no conclusive proof that they pose any threat.
For the geeky among you, here’s Wikipedia‘s technical description on how DECT works:
DECT operates in the 1880–1900 MHz band and defines ten channels from 1881.792 MHz to 1897.344 MHz with a band gap of 1728 kHz. Each base station frame provides 12 duplex speech channels, with each time slot occupying any channel. DECT operates in multicarrier/TDMA/TDD structure. DECT also provides Frequency-hopping spread spectrum over TDMA/TDD structure. If frequency-hopping is avoided, each base station can provide up to 120 channels in the DECT spectrum before frequency reuse. Each time slot can be assigned to a different channel in order to exploit advantages of frequency-hopping and to avoid interference from other users in asynchronous fashion.
For those less technical, the important thing to know is that cordless phones have a range of around 100m (though some manufacturers have improved on this). This range is really for line of sight communications, so you’ll get less than this indoors, but still enough to wander around the house making your calls. The other awesome fact is that DECT signals operate fine in the relatively congested radio spaces we occupy (Wifi, Bluetooth, baby monitors etc cause little interference to their operation).
What a lovely world we live in huh?