A "Sound" Delivery Van
Page 57
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MANY vehicles are now being equipped for broadcasting, speechamplifying and record-producing, but the latest which we have inspected is even more comprehensive in its accomplishments—and, withall, the ,necessary equipment is so compactly arranged that ample floor Space is available for the carrying of goods. The equipping a this interesting vehicle has been carried out by GramoItadio, Ltd., Commercial Works, Church, near Accrington, and it embodies patented apparatus developed by the company. Its. external appearance is merely that of a large-capacity boxvan ex
tended over the driver's cab. Rear louvres are the only sign that it is in
any way different. There is also a space over and at the back of the cab, and a large orifice in the floor of the extended portion. These constitute part of the scheme, because the arrangement acts as a sound amplifier.
As a reproducer, either of broadcasting or records, it is enormously powerful, and it is claimed that at full volume it can he heard distinctly at a distance of three miles. A noteworthy part of the equipment is the projector for cinematograph films or lantern slides. The daylight screen, which is immediately under the speaker louvres, is hinged and can be supported against the roof to permit free space for loading. Provision can be made for elevating or extending the roof above its normal height so that the screen can be raised and thus be seen by more people. Provision can also be made for increasing the dimensions of the picture by telescoping one van body inside or outside the original, the portion extended being exponential, to give a greater screen area, whilst two or more pictures can be obtained from the one projector by the use of prisms.
The loud speaker is a logarithmic horn, 14 ft. long and mounted under the roof of the van. It is operated by an air-cooled, electro-dynamic reproducer able to dissipate 3 ohms, without overheating.
Microphones are carried and demonstrations can be given on the tailboard of the van, of a microphone can ho carried to a distance of half a mile or more on its flex, without the quality of the reproduction being impaired, whilst films can be reproduced with a running commentary, or lantern slides shown accompanied by suitable music. There are also slides for community singing. By the provision of a double fader, gramophone records can be played and comments interspersed from the microphone. A second microphone permits cross-talks. To provide for the playing of dance music there are two record turntables, the motors of which run in oil. These can be operated while the vehicle is travelling.
A voltage of 550 is provided by a specially wound dynamo driven from the engine and provided with a mechanical cut-out.