The heavy Maschinensatz A generator set supplied electricity where no mains power was available. A petrol engine drove a generator, a machine that converts the engine's mechanical motion into electrical energy. This allowed electrical equipment to operate independently of a fixed power supply.
The set could be transported on a trailer, allowing the power supply to be moved to another operating location.
Additional chargers also allowed rechargeable batteries to be charged. Contemporary German documents referred to these batteries as “Sammler”, or accumulators.
Maschinensatz C – small generator set
The Maschinensatz C was a small petrol-driven generator set. Different versions supplied power to signals equipment or charged batteries. The engine drove a generator that produced electricity.
The battery-charging version was called the Lademaschinensatz C. It had an LG 650 direct-current generator driven by an air-cooled two-stroke engine running on a mixture of petrol and oil.
The versions differed in power output and voltage. Specifications for one version therefore cannot be applied to every set carrying the designation C.
TFb1
The TFb1 allowed an additional telephone conversation to be carried over an existing telephone line. The same line could therefore carry an ordinary call and an additional call at the same time.
The set converted the electrical speech signal to a higher frequency range. At the other end of the line, a second set converted it back into an audible conversation. Filters kept the two calls separate.
This method is called carrier-frequency telephony. The TFb1 used a carrier frequency of 5.5 kilohertz and operated in the 3.5 to 7.5 kilohertz band.
Verstärker 38 (V38) – telephone repeater
The Verstärker 38 amplified electrical speech signals on telephone lines. These signals weaken as they travel along a long line. The repeater restored their strength, making calls possible over greater distances.
The set used thermionic valves and was powered by 12-volt rechargeable batteries. An additional device supplied the higher voltage needed by the valves.
The gain had to suit the particular line. Measurements established how much the line attenuated the signal. There was therefore no single fixed range: it depended on the line and the repeaters used, among other factors.
MEK 8
The MEK 8 was an AEG system that could carry up to eight telephone calls simultaneously over one wire pair. A wire pair consists of two associated conductors, so eight separate pairs were not needed for the individual calls.
The system used carrier-frequency telephony. Each call was assigned its own channel in a different frequency band. All the channels travelled along the line together.
At the far end, the receiving equipment separated the channels and converted the signals back again, allowing users to hold their conversations independently.
Klappenschrank – manual telephone switchboard
The Klappenschrank was a manually operated telephone switchboard. The version described here could accommodate ten telephone lines. An operator established the connections requested by callers.
An incoming call was indicated by a falling shutter. The operator answered, asked which connection was required and connected the lines using plugs and cords.
After the call, the connection was released and the lines became available again. This system did not provide automatic dialling like a modern telephone.
Cable-testing vehicle
The cable-testing vehicle carried instruments for examining communications lines and locating faults. One version was the Kabelmesswagen Kfz. 61, built on a standardised chassis.
Tests checked the electrical connections and whether the line insulation provided adequate protection. Damaged insulation can allow current to flow along unintended paths and disrupt communications.
The instruments were connected to the lines under test. Their readings helped locate faults and prepare repairs. The vehicle carried the necessary equipment to the work site.
Line-testing bench
A line-testing bench was used to examine communications lines and the signals carried over them. Several instruments were used. A test-signal generator produced a signal of known strength, while a level meter measured its strength at the test point. “Level” here means signal strength.
Comparing the readings showed how much the line attenuated the signal. These measurements helped check transmission quality and adjust repeaters correctly.
Further electrical tests could be made with the Feldprüfschrank 35 field test set, which contained voltage- and resistance-measuring instruments. It could be used with the Feldklinkenumschalter switching unit or as a stand-alone test set.
