Improvements in and relating to light-controlled optical systems

摘要

432,789. Signalling by light. SEIBT AKT.-GES., DR. G., 54, Feurigstrasse, Sch�neberg, Berlin. April. 15, 1935, No. 11562. Convention date, April 14, 1934. [Class 40 (v)] A light telephony or signalling system employs a lead sulphide contact or like cell in conjunction with lenses which are chromatically or spherically corrected for the infra-red range of 1.2� to 2.5�.