The drive unit consisting of two ring-connected segments contains in addition 
to the electronics for the camera function control the components for the film pressure 
plate function (vacuum pump and lifting magnets) as well as the film transport motors. 
It remains on the mount so that the modular parts to be moved, namely lens cone 
and cassette, could be freed from the mentioned components and thus reduced in their weight 
A checkboard with signal lamps on the drive unit serves for indicating the status of 
the cycle run and, in case of need, for locating faults in the instrument. 
The principle of the control unit as a separate equipment with fully centralized 
operating and control functions corresponds to the proven MRB system. The number of the 
indicated elements was however increased so as to give the operator the possibility to 
optimally control the running functions or to check those functions to be influenced by him. 
The levelling of the mount of the control unit is automatically transferred to the 
universal joint of the camera mount, same as the azimuthal rotation of the control unit 
for drift correction. The latter is made in the well-known manner by visually matching 
the motion direction of the terrain image on the screen of the projection system with the 
engraved course lines. By means of a reversing prism system incorporated in the path of 
rays of the projection system a synchronous motion of the ground image with the natural 
motional direction resulting from the aircraft motion is achieved, so that the operator's 
reorientation is no longer necessary. 
Visible on the ground image is also the well-known endless tape with moving marks, 
whose synchronism generated by visual match supplies the v /h_ ration required for the 
functional control. This ration enters the calculation of9bofh the camera cycling 
rate and the image motion compensation. 
The indicating panel of the control unit shows in digital from the f-stop setting as 
well as the exposure times, both the one required due to the exposure measurement and the 
one set in the control unit. The setting operation proceeds automatically, after the film 
sensitivity has been input and desired f-number selected. For this purpose the computer 
ascertains a representative minimum value from one block each of brightness values, which are 
supplied by the sensor located in the lens cone. The sequence of the minimum values is 
subjected to a smoothing process, which is designed so, that the system essentially responds 
only to larger or long-term minimum value changes. On the basis of the given effective Bi dM 
emulsion sensitivity the computer determines-the necessary exposure time for the f-stop É | 
setting and adjusts the shutter appropriately. If the setting range is exceeded, the f-stop ET = NH 
setting is automatically corrected. Should the total range of-stop/exposure time not suffice, - E | | 
the next possible value of the exposure time is used and the discrepancy relative to the : | 
nominal setting signalized by a blinking light. The automatic exposure system is capable 
of being switched off, so that the parameters can also be set by hand. | 
When the image motion compensation is switched off, the amount of image motion to be 
expected on the basis of image speed and exposure time set is digitally indicated to the 
operator. Indicated is also the degree of forward overlap which is generally identical with ) bi 
the preselected value. However, the indicated actual value deviates from the preselected == 
value, when the calculated cycling rate cannot be realized by the system. The camera cycle 
then proceeds in the possible minimum time. The resulting smaller overlap is indicated and 
signalized by blinking. This is effected, when the main switch is switched to the "series 
exposure" mode. Another operating mode is the "minimum cycle' in which a preselected overlap 
is intentionally dispensed with and which is applied when in photography the largest possible 
overlap is to be achieved. A third operating mode ''single image' is intended to be used for 
taking pinpointed single photographs. 
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