GPO Vehicles

Make	Bedford
Model	OWB (B28F)
Type	Public Telephone Office
Body Builder	28 seater bus
Use	Mobile Call Office - Purchased 1946
Registration Numbers	HLA 227 & HLA 228
Fleet Number	9218 to 9223 (HLA 223 - 228) 1946
Date of picture	HLA 228 - 1955 and HLA 227 - July 1957

These vehicles were produced after 2nd World War and were rebodied.

The GPO purchased 5 coaches, in 1946, but it cannot be confirmed if they were all exactly the same type.
The purchase was made in 1946 and were HLA 223 to HLA 228. It looks like these were ex-WD vehicles.
HLA 228 was rebodied by Kidbrooke as a Mobile Call Office in 1955.

An article from
The Post Office Telecommunications Journal
August 1955

First Mobile Call Offices launched

The first group of public telephone call offices on wheels in this country was driven in June from London to Norfolk to open for service at Norfolk Agricultural Show. Its official name is the 'Mobile Telephone Unit' or 'Mobile Call Office Unit'; colloquially and popularly it might well become known as the 'Telebus'.

Although the new unit started service at an agricultural show, it was planned and has been built primarily for providing telephone service in emergencies. Within a few seconds of the Harrow railway disaster in October, 1952, the telephone services in the neighbourhood were congested with calls for doctors, medical supplies, ambulances and hospitals, and by control calls from the railway people and the police. The Post Office then realized that a mobile unit, containing several call boxes which could be rushed to such scenes and plugged in, would be immensely valuable.

The Engineering Department Motor Transport workshops at Kidbrooke acquired a Bedford chassis from a disused coach. They rebuilt the coach, modernising the overall lines and making booths for telephone positions, which can be used either on a direct exchange line or a coin box basis, with cupboard space for components, and they installed interior lighting, two ventilating fans and treated the walls and ceilings with sound absorbing material. Stabilising rods were fitted to reduce movement and bounce.

The London Power Section workshop panelled the rest of the interior with 'Wearite' and provided cushioned seats in the booths, and the London North Area Telephone Manager's installation staff fitted telephone wall boards and a switching panel.

Finally, the coach was painted and embellished - Post Office red, gold and black - in the Engineering Department's workshop at Yeading.

By key switching in the attendant's booth, the telephones can operate to C.B. manual or automatic exchanges, including unattended automatic exchanges (except type Nos. 5 and 6); C.B.S. and magneto working are not catered for. The attendant's booth contains a telephone for service to the exchange staff.

When the coach arrives on the spot, a 15-pair polythene cable will be laid over ground to the nearest permanent line plant. More than 60 yards of cable are carried.

Power for interior lighting, and for driving the ventilator vans is drawn from the car battery, which is considerably larger than would be needed merely for starting and exterior lighting. A small charging set is included for the larger charging rate. An A.C. mains source, instead of the 12-volt battery, can be used for lighting and ventilation.

The vehicle is exceptionally neat and compact. The overall length is 24 ft. 6 in., and the width 7 ft. 6 in. The wheel base is 14 ft. 8 in. long and 7 ft. wide.

The unit will work in the London Telecommunications and Home Counties regions. It will attend such events as agricultural shows only when not called on for emergencies but, should the need arise, it can be pulled out and rushed at once to the scene.

An extract from the
The Post Office Electrical Engineers Journal
Volume 48, Part 3 - October 1955

An Mobile Call Office Unit

A description of the mobile call office unit which enables the London Telecommunications Region to provide temporary telephone service quickly on a substantial scale.

Introduction
There are frequent demands for temporary telephone service at race meetings, agricultural shows, etc., and also, happily infrequently, there is the need to provide urgent telephone facilities at the scene of a disaster, of which the Harrow train wreck and the East Coast floods are fairly recent examples.

The normal methods of meeting such demands have been to install call office equipment in cabinets or kiosks, or to provide a rather crude arrangement of a few telephones on tables, often in poor accommodation. A better solution was provided by the Home Counties Region in designing the portable telephone cabinet previously described in this Journal, but this cabinet requires to be crated for transporting and time must be spent in erecting it on site.

The London Telecommunications Region therefore prepared a scheme for a self-contained mobile call office unit, providing ten telephones and an attendant's position. This was considered to be the maximum that could be accommodated in an available type of medium-sized vehicle and so avoid the need for purchasing a special vehicle.

A 28-seat single-deck bus on a Bedford chassis, and of war-time utility construction, was made available to the L.T.R. for conversion to a mobile kiosk unit; the work of converting this vehicle being arranged by the Motor Transport Branch of the Engineer-in-Chief's Office and carried out at Kidbrooke Central Repair Depot (C.R.D.), with exterior decorations and signwriting by Yeading C.R.D.

Construction and Fitting of the Unit
The vehicle in its original form had an entry at the nearside and an emergency exit at the rear. The exterior panels, of steel sheet, were in 'lobster back' form to avoid panel beating at the roof corners, and the usual flaring of the bonnet to the front of the bodywork was omitted. Interior head-room was a bare 6 ft.; seats had wooden slats instead of cushions and few of the side windows opened.

It became apparent at an early stage that a simple conversion would not be practicable, and it was therefore decided to strip the vehicle body to floor level and rebuild it to suit the new requirements. On this rather old chassis, an elaborately curved bodywork exterior was considered unlikely to be aesthetically satisfactory and it was, therefore, thought best to aim at simplicity. One particularly awkward problem was to decide how best to arrange the side windows which, due to the size of each cubicle and the position of its telephone, had to be narrow and rather high from the floor level. The difficulty of arranging the windows was further aggravated by a decision to raise the internal head-room to 6 ft. 8 in. This abnormality was disguised to some degree by using 'plant-on' window frames with the frames anodised bronze in colour and by providing a wide waist moulding, similarly anodised, placed well below the window level.

A 2-in. thickness of glass fibre insulating material has been inserted between the inner and outer panels of the vehicle to give both thermal and acoustic insulation. The inner lining is perforated so that the insulation can be effective acoustical^. Natural ventilation is obtained by extractor-type roof ventilators, controlled from the inside, and by sliding top windows in all but the end pair of cubicles; ventilation for these is provided by a drop window in the rear door. Two electric fans, extracting air from the vehicle, are fitted above the windscreen, and the expelled air reaches the outside via two venturi louvres fitted with internal waterproof baffles in order that the fans may work regardless of weather conditions.

Bracket-type lamps are provided in each of the cubicles and at the attendant's position. Flush-type lamps are also fitted along the centre gangway and in the steps of the entry and exit doors. Three 70-A.H. batteries wired in parallel are sufficient to run the electric lights and fans for a long period but provision is made to couple direct to electric light mains, if available, via a transformer. The batteries may be charged by a 500W portable petrol-driven generator, normally stowed under the floor, and a weather-proof cowl is provided for the generator in order that battery charging can be carried out regardless of the weather and with the generator remote from the vehicle. The generator and cowl can be seen in Fig. 4

To avoid disturbance of the coin box mechanism due to movement of the vehicle by people entering and leaving it, steel stabiliser props may be added to each corner of the vehicle when on site. Stowage space for all equipment associated with the vehicle is provided in lockers under the floor with the exception that two portable wooden platforms, used as steps in front of the doors, are carried in canvas envelopes strapped to the vehicle floor.

The cubicle partitions and seating arrangements were built jointly by Kidbrooke C.R.D. and the L.T.R. Power Section, Cornwallis Road.

Telephone Equipment in the Unit
For the majority of occasions when the Unit will be used in the L.T.R., connection is required to C.B. manual or automatic exchanges, including U.A.X.s; the standard Jubilee-pattern wall board, including a Bell Set No. 40 (modified) and a Telephone No. 238(L), has therefore been fitted. The two boards in the booths at the rear end of the vehicle were, however, cut and installed without the parcel container because the full width required was not available.

Simple arrangements are necessary to allow the unit to operate to either a C.B. manual or an automatic exchange, and for use at the scene of a disaster it is necessary to cut out quickly the coin box mechanisms.

A key switching panel, fitted in the attend' ant's booth, has therefore been included in the wiring to the individual telephone circuits.
The circuit arrangement (Fig. 5) is based on the standard diagram for conversion from C.B. manual to automatic working but includes an additional key (KB) to cut out the coin box circuit when direct exchange line working is required.

The attendant is given an exchange line over which advance bookings of calls and other service arrangements can be made without interruption to the ten public lines.

P.V.C.-type cable, run in conduit, connects the key panel via fuses and protectors for each line to a simple, robust line terminal board, which is fitted in a locker with external access at the near-side front of the vehicle. From this point a 100-yard length of 15-pair polythene cable, provided with the unit, can be connected by the local staff to the selected distribution pole or box. The spare pairs in this cable are bunched and used to extend the telephone earth from the D.P. to the Unit, where it can be bonded to the earth spikes provided for earthing the chassis of the vehicle.

Conclusions
The mobile call office unit is garaged in the North West Area of the L.T.R. and is available for use by other Areas. At the time of writing this article, the unit has been in service at the Norfolk Agricultural Show, Norwich, and at a race meeting at Alexandra Park. Experience has shown that adequate provision has been made for securing all portable items and spare equipment in containers or lockers and for clipping the telephone handsets in their normal rest position during travelling. The apparatus has travelled well and no undue maintenance has been required.

Acknowledgments
It is desired to record acknowledgments of the work of the Motor Transport Branch staff at Kidbrook and Yeading C.R.D.s and of the L.T.R. Power Section. The close co-operation of the Motor Transport C.R.D.s, L.T.R. Power Section and L.T.R. North Area's installation staff to ensure that fitting and wiring of the lighting, ventilation and telephone apparatus was carried out in conjunction with the installation of the panelling inside the vehicle contributed greatly to the satisfactory construction of the unit.

HLA 228