Instructor call system for language laboratories - with built-in call signal control both auto and by the instructor

摘要

The system employs optical signals visible to both the student and the instructor. The signals are produced by the student and both signals have a duration limited by a storage device. Any call signal can be maintained active for as long as desired by establishing voice contact between student and instructor. Pref. any call signal can also be cancelled at any time. A switch may be provided at the instructor's console to prevent selected call signals from appearing, e.g. by means of a mechanical diaphragm.