System for electrooptical information transmission

Abstract

In a system for the transmission of information between an inquiry station nd a response station by means of optical radiation from the inquiry station an outgoing signal is transmitted and subjected to a modulation partially in fixed frequency and partially with information code and by the response station on the one hand is received and evaluated and on the other reflected back as return signal and subjected to a modulation. The enabling of the return reflection is controlled in dependence upon the evaluation of an identification contained in the outgoing signal. The instant of the enabling is controlled by a coding contained in the outgoing signal which indicates the end of the transmitted message, whereupon at the start of the return reflection at first an acknowledgement signal, for example an unchanged reflection of the coding of the outgoing signal, is transmitted and by said acknowledgement signal the switching of the inquiry station to fixed frequency and/or fixed coding is automatically controlled, a ready-to-answer status thus being produced. In the response station means are provided for recognizing the fixed frequency or fixed coding of the outgoing signal and for producing an operating readiness of the modulator of the response station tuned to said fixed clock frequency. An automatically controlled electromechanical diaphragm may be provided for protecting the optical system and permitting electrooptical addressability only when the inquiry code is decoded as friend signal.