On Sun, 24 Aug 2003 20:46:40 +0100, Martin Angove
wrote:


1: REN is much less of an issue these days because most phones
seem to be less than 1 REN even though they may be marked 1 REN. I have
had five ordinary phones, one minicom and one computer modem attached
together, and never had any ringing problems. Might be helped by the
fact that I use master sockets throughout rather than extensions?

That will make no practical difference.

2: There is just no comparison in the quality of the signal. I have all
wired phones in my house, some of them cheapy-cheapy jobs, but the sound
quality on them is vastly better than from any of the DECT phones my
friends own - expensive or not so.

Others experience might be different. Certainly I can detect no
difference in the sound quality or volume between my DECT and normal
phones. However some DECT phones are smaller than conventional ones
and positioning them is (as with mobile phones) more critical than
with most wired phones. Some Phillips DECT phones do appear to have
low volume levels (but so do some wired phones).

2a: (related) DECT phones aren't much good for hearing-aid users (they
have similar problems with some mobile phones). The earpieces aren't
designed to make use of the aid's microphone(s) and when the aid is
switched to "T" (the induction loop setting which works fine with 99% of
cheap phones) the aid can suffer dreadfully from RF pickup ("bzzzzt
bzzzzt bzzzzt" noises).

There are (rare) DECT phones designed for hearing aid users.
Alternatively you can use one of the many DECT phones with a headset
socket and something like the Plantronics M130 headset which works
with induction loop hearing aids.

3: Don't (some?) DECT phones work on the same frequencies as... erm...
wireless networks? Wireless security systems? Wireless remote control
systems? Wireless video senders?

No, DECT operates on the 1880-1900 MHz frequency band. Wireless
network, video senders etc work mainly at 2400MHz. Alarms use a
number of frequencies mainly in the 400 and 800MHz region.

4: Isn't there a limited number of discrete channels available to a DECT
phone (16?) What happens if everyone in your cul-de-sac has DECT phones?
Oh, I forgot, they only work reliably up to about 50m ;-)

Mine happily work to 70m, but interference is never likely to be a
problem. DECT uses Time Division Multiple Access and has 10
available carriers. There are 24 time slots available (12 in each
direction) within each 10ms frame. DECT uses dynamic channel
selection to minimise interference. Channel assignment is done by
finding the lest interfered channel and channel reassignment can
take place during a call. Effectively 120 dynamically allocated
duplex channels are available to any DECT device. This gives a
potential traffic density of about 10000 users per km 2 without the
need for frequency planning.

5: If I carried a phone around in my pocket/on my belt all the time I'd
sit on it, or drop it or otherwise mutilate it, and it'd never get
charged, so it'd have to live on the cradle anyway which makes it hardly
any more convenient than a wired phone!

DECT phones are quite low power, mine usually go all day off the
charge cradle and with several hours use a day battery life is never
an issue. 10 hours talk or 120 hours standby are fairly typical.
Finding the phone sometimes is an issue :-) they all migrate to one
place which is always the other end of the building from where you
are when the phone rings.


--
Peter Parry.
http://www.wpp.ltd.uk/