7 is of triangular shape and has a perforation 11 in the middle this triangular baseplate 7 is constituted with flange segments at the corners furthermore a connection is constituted with the baseplate 7 for an optical element here a deflecting mirror which rests on abutment points 13 a mounting structure 5 is formed by the baseplate 7 with the reinforcing ribs 8 and the connection for an optical element 13 the baseplate 7 has three support points 17 for a telescope an optical signal can be sent and received by means of the telescope not shown the telescope is arranged so that its optical axis 35 runs perpendicularly of the baseplate 7 as shown in fig2 a received signal or a transmitted signal is shown in fig2 by the double arrow 33 the optical axis 35 is likewise drawn in a signal received by means of the telescope passes through the perforation 11 and is reflected at a deflecting mirror 16 which is mounted by means of the mounting points 15 in the direction of a seating 19 this seating 19 is constituted as a hollow body and has an aperture 18 for the coupling ion of the received signal 32 this coupled in signal is supplied to a receiving unit 25 which has an optical axis 37 and which is firmly secured to the seating a transmitting unit 23 with an optical axis 39 which is arranged parallel to the optical axis 27 of the receiving unit 25 is likewise secured to the seating 19 the signal emitted by the transmitting unit 23 is first conducted within the seating 19 and is reflected by a deflecting mirror 27 with a surface normal 41 which represents the optical axis of this deflecting mirror 27 to a.