Bjarne Jensen, the proprietor of a Danish radio and railway museum has very kindly sent me a scan of an early Telavox catalogue.
Here is Bjarne's website:
Funder.Nr.Hede Banen & Funder Radiomuseum -
Dating from 1942-43 the catalogue shows typical Telavox clocks of this period but emphasises the time switch options available to fit these standard cases by fitting a special backplate and contacts at the factory:
The chart depicts the increased accuracy from using a bimetallic torsion balance. My rough translation of the Danish text appears in italics:
As is well known any clock which is not furnished with special arrangements will lose in warm condition and gain in cold. But the Telavox balance, as can be seen, compensates for all variations in temperature. Moreover all of the parts concerned with the timekeeping of the Telavox movement are made to a tolerance of 1/100th of a millimetre. Which provides a sound basis for the accuracy of Telavox timekeeping. The time switch mechanism (patents applied for) is different from all previous devices in being provided with a form of double contact. Which improves contact reliability many times over. The contact materials are of riveted gold and silver. The clock will run for a year on the 3 Volt "Hellesens" battery provided.
There must be those who have missed a (radio) transmission. They will have wanted to enjoy a programme but have been sidetracked by something else and forgot to turn on the radio receiver. The previous pages have described the Telavox battery driven clock but it is also possible to have a time switch fitted which will turn the radio on and off for you. The time switch, which is remarkably easy to set, can turn the radio on and off at 5 minute intervals over the full 24 hours. So one can easily set the time switch to turn the radio on and off at the beginning and end of a particular radio programme which one wants to hear. A discrete, patented backplate on the clock leaving it looking just like any other beautiful table or sideboard clock. Another option is to have the clock running from the mains [using an 'LK' Synchronous movement] instead of a battery movement.
The Telavox battery driven clock, with time switch, is a universal device and can be adjusted without the removal of any parts for a variety of voltages. It can work with 110, 150 and 220 Volts DC and 170-220 Volts AC. It can be ordered, without any extra charge, to run on 110 Volts AC. So it is not necessary to adjust it to 150 Volts AC. The synchronous motor model can, with a simple adjustment, run on 127 or 220 Volts AC.
All battery clocks are delivered complete with a battery. 12 setting pins for the backplate time switch are provided.
A written guarantee for one year is provided against material or manufacturing faults. Though not for the battery.
Extra time switch setting pins are available at 0.25 Danish Kroner each.
A new Hellesens battery, Type 57, is available at 2.63 Danish Kroner each.