1. What is DECT?
DECT is short for: Digital Enhanced Cordless Technology and these days, all cordless home phones tend to be called DECT phones for convenience and all operate to the DECT standard. There is a protocol within the DECT standard, called GAP, which is an important feature described further down in this guide.
2. Why Digital?
In the old days (only a very few years ago!) we only had "analogue" phones, even the cordless ones available then. Technology was such that these were "state of the art" (for their time). The wireless technology was much like FM radio and the phones would transmit and receive their signals via some very old fashioned ariels - telescopic, just like your portable radio. The same held true for mobile phones and until very recently, TV & radio.
There were only a few radio "channels" or frequencies available and wireless phone calls were prone to interference and signal degradation. You could have real problems if you lived in a block of flats, where there might have been 20 or 30 tenants, all attempting to use the same type of equipment!
These days, everything has gone digital - cameras, camcorders, mobile phones , TV, Satellite, and since around 2005, cordless home phones. The wireless technology is much improved, with now literally 100's and 1000's of channels available within a defined radio frequency.
The way that the signals are transmitted has also changed, with "packets" of data being sent in "bursts" (in encrypted format so no-one can eavesdrop on your call). Modern equipment has in-built error correction, so that when your signal is converted back into voice at the other end nothing is lost in translation.
The phones are much smaller and almost as sophisticated as mobiles, although we have yet to see a signifcant increase in the availability of video calling - this has been largely overtaken by mobile 3G techonology, which telecoms companies like BT, Vodaphone and '3' paid billions for the licences just a few years ago.
The future for home phones (and for many on the move), is more likely to be through "Internet Telephony" or VOIP (of which more in another article).
3. What is GAP?
The GAP (General Access Profile) protocol is a standard within DECT, that allows any such enabled DECT phone to 'register' with any other similar GAP enabled system. The manufacturers may not be keen to advertise the fact but a GAP enabled DECT phone should be able to communicate with ANY other GAP enabled system - regardless of who manufactured the phones! Some facilities may not be completely available in all cases but basic communication is guaranteed by this protocol.
In reality, fashion dictates that our nice shiny new DECT phones look alike, plus if our system has fancy features, so as consumers we might tend to buy additional handsets of the same type & model - where available. However, as with mobile phones, new models replace existing ones almost every week it seems, so it's good to know that we can add to or replace any GAP phone with any other of a similar proctocol.
This facility benefits the consumer in that we can start off with one unit, which wiil always have a base station (the one you plug into the phone wall socket). When we want to add more, then depending on the make & model, we can add up to 5 more handsets (6 in total), all running off the same base station! Manufacturers often produce generic types of additional handsets, which are compatible with a wide range of systems (some systems have quite a lot of extra features - for a price - that not all consumers want, need or wish to pay for).
It is also useful in that the BT requirement for their telephone system is for a maximum REN number of 4 ( REN stands for Ringer Equivalence Number). In the old set up, each phone plugged into a socket would have a REN of 1 making a maximum of four phones allowed. (You could put more in but BT would not guarantee that the phones would ring out corectly and, in the event of a system failure at the exchange, you might be held liable for any damage caused!). Some fax machines and older type answering machines have a REN of 2 or more in some cases, which would limit your options considerably - maybe even requiring a second line.
DECT phones don't have that problem, as only the base station is connected to the phone system.
NB However, note that if you buy a non-GAP enabled DECT phone, then you will NOT be able to add additional hanndsets, to go with your original set-up, so you would need either to ensure that the phone is GAP capable, or make sure you buy a twin, triple or (where available) a quad pack in the first place.
Most DECT phones are also GAP enabled (even though it is not always mentioned by manufacturers) - the exceptions are usually highlighted in the product specifications or descriptions.
(c) 2006-11 MPRC Revised 03 May 2011