In July 1981 System 4 was launched in London, initially sharing the same freq allocation as System 3 but with 12.5 Khz FM, it had 110 channels to play with when System 3 was finally switched off in Jan 1986.
It was based on a system from TeKaDe, and trialled in Nuremberg
163.0375 to 164.425Mhz (split -4.5: 158.5375-159.925) channels U001-U111
System 4 was the first UK radiophone service to allow the user to set up a call themselves without the aid of an operator.
It was also the first system where duplex speech was the norm on all handsets.
I found some interesting snippits at http://www.digitalarchives.bt.com/web/arena/results?p_p_state=normal&p_p_lifecycle=1&p_p_action=1&p_p_id=crDetailWicket_WAR_arenaportlets&p_p_col_count=2&p_p_col_id=column-1&p_p_col_pos=1&p_p_mode=view&search_type=solr&arena_member_id=27203311&search_item_id=a23386d6-19e7-4304-ba7e-e9bc21f819e9&agency_name=AUKC00001
Page 34 of the Archive says
Most of the work in the UK for the automatic radiophone service (TeKaDe, System 4) is now on schedule
4 July ready for service date
end of march acceptance testing in Nuremberg factory
Page 46 of the Archive says
Demand for radiophone in the provinces on system 3 remains low, despite spare capacity in all service areas
System 4 invites sent to first 2000 on london waiting list .. Invites sent 6 months ago 47% acceptance, 80 % opting for auto rather than manual service. 5 companies have offered BT 6 carphones
On page 57 of the archive
Moaning about CB and
pre-acceptance testing on system 4 completed 20k calls made, 14 call failures
Page 78 of the archive
End of July 70 customers !, growing at 26 per week
On the 16 October there were 477 customers, faint speech problems
Who are BS5 ?
Radiophone system 4 comes to Solent, with circuits from Birmingham RCE (radio controlled equipment)
Storno mobiles causing distortion problems
London System 4 "working well", "faint speech problems overcome"
System 4 now has 941 subs
System 3 has 7,398 customers (1,198 in London, 5200 in the provinces)
System 4 has 924 customers all in London.
1000 customers on the waiting list will be offered service next month
The Introduction of the automatic radiophone service in London enabled 1200 customers on the waiting list to be offered service during March
Page 149 june 1982 date
Radiophone 27k below budget due to slower than expected take up of service
2000 invites sent out, 600 asked for service
now over 1000 subs
Subscriber unhappy about "call limitation" feature that cuts off calls 20 secs after warning tone.
3 minute parameter has been extended to 6 minutes
1704 subs connected to system 4
2095 system 3 users in London, 5179 in provinces
system 4 failed on the 27 July and 5 august
BT buy 1500 carphones from pye
New tariffs to be introduced in November
Calls to system 4 radiophones as well as calls from system 4 radiophones were 8s per unit (4.3p or 5p phone box)
In 1971 it was £7.50 per qtr
In august 1978 the cost of a radiophone was just £15 per qtr http://www.london-gazette.co.uk/issues/47614/pages/9686
in august 1980 it was £20 per qtr
10 July 1981 it became £40 (system3) £100 per qtr (system4)
Prices increased 32% November 1st, 9500 letters sent out
System 4 trading loss only 4 k in November, but no spare capacity in London
year to date loss £646k
mailshot of 5000 in severnside, only 1 customer gained
Premium service called "Telecom Diamond" to charge more to wealthy and vociferous on waiting list and combat illicit trading in radio phone numbers
December £15 k profit on radiophone
London system 4 full
Major effort to improve system 4 quality of service
The Mobira MC25 UK System 4 Radiophone control panel
Other System 4 mobiles include
PHILIPS M9140/F9540 SYSTEM 4 RADIOPHONE
more info http://www.storno.co.uk/radiophone.htm
1983 prices here http://www.christopherlong.co.uk/pri/carphones.html