Slab Desynn

If the voltage at the 3 tappings of the transmitter of a basic Desynn are measured as the wiper arms are rotated 360°, it will be seen that they produce a sawtooth waveform as opposed to a sinewave. 
This results in the pointer of the indicator not following the transmitter exactly.  In most instances the difference is insignificant, however their may be certain circumstances where it cannot be overlooked.

The solution is to use a modified Desynn transmitter called a 'slab Desynn'.  In a slab Desynn, the resistor is wound on a slab former and has the power supply connected to it, whilst the wiper arms now provide the output to the receiver, there being 3 wiper arms each displaced from the next by 120°.  The output from this device is a sinewave.  It can be connected to the same type of indicator and operates in the same way as the basic Desynn.

Synchronous Data Transmission

Synchronous data transmission systems are designed to indicate the position of a component or control surface that cannot be directly observed.  The systems fall into one of two categories; d.c. systems called 'Desynn Systems'

There are a variety of different types of Desynn systems available:

The Basic Desynn is generally operated by a rotary motion, however linear versions are also found.  The conversion from linear to rotary motion being achieved by a push rod and gear wheel.

The Micro Desynn was designed to magnify the small movement obtained by such items as pressure measuring devices.  They are operated by linear motion.

The Slab Desynn was designed to overcome signally errors inherent in the basic Desynn system.  In the vast majority of instances the errors in the basic Desynn 

Basic Desynn

 

In the basic Desynn system the transmitter comprises an endless resistance wound on a circular former, this arrangement being referred to as a 'Toroidal Resistance'.  Equally spaced at 120° intervals around the resistor are 3 tappings, it is to these that the signal wires are connected.  Running on the resistor are two wiper arm type contacts that are spaced apart by 180° and insulated from one another, it is to these that system power is applied.

The indicator comprises a two pole permanent magnet rotor, pivoted to rotate inside a soft iron stator, the pointer being attached to the spindle.  The stator carries three star connected windings that are connected to the three wires coming from the tappings of the transmitter.