Terrestrial Trunked Radio (TETRA)
81. In March 2000, BT announced a £2.5bn contract
to roll out a national digital radio service for Britain's police
Based on the Terrestrial Trunked Radio (TETRA) digital standard,
BT's 'Airwave' service is intended to provide secure and fast
radio communications network for the emergency services. BT stated
at the time:
"This initiative will deliver improved efficiency
and greater co-operation between the nation's emergency service
teams and the wider public safety community, brought about by
a modern, efficient communications service".
The roll-out of the service is to be phased with
completion expected by 2005. A pilot service with Lancashire Police
is currently underway.
A recent Written Answer states that the main evaluation began
on 19 March 2001 in Lancashire, with a report due in June
2001, followed by national implementation.
It is estimated that around 3,000 masts will be needed to provide
the necessary geographic coverage and capacity.
BT said "in keeping with the spirit of the precautionary
approach and mindful of public concern, we will commit to locate,
as far as possible, new base stations that minimise their social
impact on the local community".
Mast Action UK told us in a supplementary note that some of their
members were already experiencing problems with planning applications
for TETRA masts.
82. TETRA is an open standard for digital private
mobile radio. It is approved by the European Standards Institute
(ETSI) and used by public safety organisations throughout Europe.
TETRA terminals utilise 17.6 Hertz, or 17.6 'pulses' per second.
BT's Airwave base stations "emit a continuous tone which
is not amplitude modulated".
Amplitude modulation is defined as the variation of the power
level radiated from a radio transmitter.
The TETRA terminals used Time Division Multiple Access (TDMA)
to enable up to four users to access a single TETRA radio channel
simultaneously. It is this that produces the 'burst' of energy
from the terminal at the rate of 17.6 times per second.
83. BT told us that they comply fully with the guidelines
on exposure to electro-magnetic fields produced by the NRPB and
those of the ICNIRP and that, despite the references in the Stewart
Report, "no health risks were suggested in the report and
none have been identified". The Stewart Report records studies
of the effects of RF fields on calcium movement in brain tissue.
It was discovered 20 years ago that the efflux of calcium out
of brain tissue was greatest at 16Hz. The results of subsequent
studies are contradictory. The Report concluded that
"as a precautionary measure, amplitude modulation
around 16Hz should be avoided, if possible, in future developments
of signal coding".
Sir William told us that he was "pretty sure
that it will become a major facet of any future investigation.
As far as our Report was concerned, the timing was not right".
84. BT have told us that "the Home Secretary
has concluded that roll-out should continue as planned but that
in parallel, the Defence Evaluation and Research Agency and the
NRPB should undertake a review of existing scientific data".
We welcome the evaluation of the TETRA system now underway
and recommend that the results are made publicly available as
soon as possible. Whilst we appreciate the importance of
the system, we are very disturbed that there seems to have been
no examination of the evidence on potentially adverse health effects
before bringing it into service, and disregard for the
conclusions of the Stewart Report published only two months after
contract award, and drawing on over 20 years of research.