Hempenius, Makarovid, Van der Weele, Tests of Restitution Instruments 
its response is again sinusoidal [5]. Disturbances affect the amplitudes and the phase only. 
The standard input should theoretically contain the entire frequency spectrum with 
an adequate distribution of amplitudes. The amplitude ratios of the corresponding output 
and input waves, ordered according to the frequency spectrum, represent the transfer 
function of the system. 
When doing this separately for each dynamic component, the total transfer function 
of the dynamic system (linear) is obtained by multiplication of the individual functions. 
The analysis based on the distribution of curvatures is also convenient in practice. 
In this case both coordinates (Z, Y) in the output have to be considered as mutually 
dependent variables; therefore a succession of curvatures is theoretically sufficient for the 
analysis. 
The input should contain differential line elements (symbols) with all probable 
prevailing directions and curvatures. These conditions are involved in the circles with 
radii ranging from infinity to the zero. In fig. 5 the circles are ordered in a succession 
according to their size. However, in reality only one or a few sections of an infinite succes 
sion can be used as the input. The curvatures to be represented should be in corres 
pondence with their statistical occurrence in maps. This varies to a certain extent with 
the type of the terrain and scale of the map. 
Obviously the most critical performance is in the region of greater curvatures 
(smallest circles). A succession according to fig. 5 is thus convenient. 
Fig. 5. Succession of circles representing the input 
The curvatures increase non-linearly with the distances along the axis. When joining 
the successive semi circles skew-symmetrically, a connected line is obtained (fig. 6), which 
enables a continuous scanning. The line approximates a linearly modulated sinusoidal 
curve with the correspondingly increasing frequency. 
This will be referred to as a pseudo-sinusoidal curve or simply sine*-curve. Linearly 
modulated sinusoidal* curves are suitable as measuring scales for the evaluation of the 
output. 
The input is presented to the plotting system as a target, which replaces the photo 
graph. A medium contrast gray-white sine* undulated edge is convenient for the visual