It has been reported from a German source considered to be well informed,
that the batteries used for field telephones in Africa contained acid of which the
specific gravity was 24°, Baume.* For service in extreme heat, this figure is
reduced, while in Europe it would be 27° or 28°. The batteries were made of
wood, lined with an acid-proof matrix described as "pitch - tar mould". The
voltage for telephone use was stated as 1.5. After six months, the batteries
became exhausted. They resembled a single cell from a pocket flashlight battery,
of the type which usually has 4.5 volts. In this particular case, the cell was enlarged
for greater amperage.
The German signal corps is reported to be furnished with a field live-testing
set, battery operated, which can measure voltages as high as 300 amps, also
resistance. It can be used to test lines and elements, with or without load.
From the same source as the previous item comes an account of a special
cable covered with synthetic rubber, over which a tank can pass without injuring
it. Such cable is supplied in drums of 273 yards length. To lay, a truck would
drive the length of the cable on the drum, unreeling the cable, which is then
connected with the second drum, and the truck proceeds. It was stated that in this
way 2 or 3 km (1.22 to 1.86 miles) of cable could be laid in from 20 minutes to
half an hour.
The cable is reported to carry two pairs, which, it was stated, could be
used for multi-channel traffic for both teletype and telephone.
*Equivalent to 1.199 specific gravity.