I CAN only support the plea in Gavin Brett?s letter (December 19) for broadband communication in rural areas, where, if anything, it is more important than it is in densely populated areas, where resources are nearby and the option of cable may be available.

However, as published it contains inaccuracies that could mislead readers. If the mistakes have been introduced by the publisher, Mr Brett has my sympathy, as an IT consultant and writer I have suffered the same treatment many times.

The normal ?high speed? modem is rated at 56,000 bits (or 56 kilobits) per second, not 56 bits per minute ? a difference of 60,000 to one. At eight bits per byte or character, plus a little for overhead, 56 bits per minute would be about 60 words per hour, which would hardly be sufficient.

On a reasonable phone line typical speeds are between 44,000 and 48,000 bits per second, rather than 33 bits per minute, a difference of about 140,000 to one.

The ability of many sites to support a download at this sort of speed continuously is another matter, but it typically takes about four minutes to transfer a megabyte of data via a 56kbps modem if the transmitting site can keep up.

ADSL does not broadcast ? wireless networks broadcast, or it is possible to send the same data to many recipients via a communications line, but ADSL as such transmits (or receives).

Mr Brett mentions ISDN, which is not the same as dialling up using a modem. ISDN offers two 64 kbits/second channels via a normal phone line, with the option of either combining them for a total bandwidth of 128 kbits/second or using one channel for net connection, the other for voice or fax.

It is possible to arrange a fixed-cost connection for dial-up or ISDN, which actually would be almost indistinguishable from ADSL for most users. Work out how many megabytes of data per day you?d need to transfer for ADSL to be essential ? it?s a huge amount if you reckon that using a 56 kbps modem for, say, five hours a day would transfer 20MB, at least half the total hard disk capacity on most mid-range personal computers. Having said that, I?d also like to have ADSL but Okehampton is further from it than Tavistock ? the last time I looked, BT?s counter showed that we haven?t even reached treble figures.

Geoff Norman

5 Parklands

Okehampton