path 30 to the other instrument connected to reception coupling 16 for example an endoscope 24 it will be understood that this also holds for the reverse situation image transmission however is still possible despite the hermetic separation by the optical window 34 a radially projecting attachment 36 is attached to the outer side of the hollow cylindrical body 14 of the adapter 12 whose outer end is provided with a recess 37 for receiving a transmitter unit 38 the transmitter unit 38 is formed as a bar 40 whose longitudinal axis is disposed transversely or perpendicular to the optical axis 32 in a further embodiment not shown the bar 40 is rotated by 90 u00b0 and extends in the direction of the optical axis 32 three transmitters 42 are arranged and distributed over a surface on the bar 40 at each of the opposing ends namely such that the three transmitters in each case lie at the corners of a triangle the purpose of this arrangement will be described below in conjunction with fig5 and the operation of the cas system a screw 44 serves to secure and to exchange the transmitter unit 38 on the attachment 36 the relative position between the transmitter unit 38 and the adapter 12 is definitively defined and secured by this connection as mentioned above the reception coupling 16 serves to connect an endoscope 24 as seen in the illustration of fig4 the reception coupling 26 is provided to allow connection with a camera 46 the camera 46 has a coupling 48.