System 4 - RadioPhone

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

Car phones Available

British Telecom Sapphire


Philips FM95 Radiophone

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.

Bt Digitalk Archive

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

Page 46 of Deputy chairmans report

On page 57 of the archive

Moaning about CB and

pre-acceptance testing on system 4 completed 20k calls made, 14 call failures

Chairmans report page

Page 78 of the archive

End of July 70 customers !, growing at 26 per week

page 78

Page 104

On the 16 October there were 477 customers, faint speech problems

Who are BS5 ?

page 104

Page 113

Radiophone system 4 comes to Solent, with circuits from Birmingham RCE (radio controlled equipment)

Storno mobiles causing distortion problems

page 113

Page 118

London System 4 "working well", "faint speech problems overcome"

Page 118

Page 125

System 4 now has 941 subs

page 125
page 126

Page 135

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

page 135
page 136

page 144

The Introduction of the automatic radiophone service in London enabled 1200 customers on the waiting list to be offered service during March

page 144

Page 149 june 1982 date

Page 161

Radiophone 27k below budget due to slower than expected take up of service

2000 invites sent out, 600 asked for service

System4 radio phone low profits

Page 163

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

page 163

Page 177

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

Page 177

Page 185

BT buy 1500 carphones from pye

New tariffs to be introduced in November

page 185

RadioPhone Pricing 20 October 1982

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

in august 1980 it was £20 per qtr

10 July 1981 it became £40 (system3) £100 per qtr (system4)

System 3 and System 4 radiophone costs compared

Page 194

Prices increased 32% November 1st, 9500 letters sent out

Page 194

Page 200

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


Page 209

December £15 k profit on radiophone

London system 4 full

Major effort to improve system 4 quality of service

page 209
Marconi Mobira MC25, control panel

Other System 4 mobiles include

Mobira Mobira BT Emerald MC25 Radiophone similar boot unit as marconi but handset, dial keys and display combined

Philips FM95 System 4 - British Telecom Saphire


Pye M4000

Stornomatic 900

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