| 摘要 |
An electronic control or data transfer system comprises a manipulatable electronic light sensor, which can sense selectively either the output of a digitally modulated light source or a bar code, and which feeds an electronic device which can distinguish whether the sensor output is derived from a digitally modulated light source (a) or a bar code (b). For thus distinguishing by producing waveforms as at (c) and (d), a differentiator and an assymetry detector sense whether the output pulses have decaying or sharp trailing edges respectively. It may comprise a light pen which can be applied to selected portions of a television screen whose light output is digitally modulated at a rate related to the field scanning rate, and to reading bar codes in a broadcasting periodical. <IMAGE> |
