Digital information storage apparatus

Claim 1

DIGITAL INFORMATION STORAGE APPARATUS COMPRISING A MATRIX OF ELECTRO-LUMINESCENT CELLS EACH CORRESPONDING TO A DIGIT LOCATION AND ELECTRICALLY CONNECTED IN ROWS AND IN COLUMNS, A STORED BINARY DIGIT BEING REPRESENTED BY THE SCREENING OR NOT SCREENING OF A CELL, AND MEANS FOR READING THE DIGITAL INFORMATION AT A SELECTED LOCATION COMPRISING MEANS FOR ENERGISING THE ROW CONTAINING THE SELECTED LOCATION AT A FIRST FREQUENCY, MEANS FOR ENERGISING THE COLUMN CONTAINING THE SELECTED LOCATION AT A SECOND FREQUENCY, AND A LIGHT SENSITIVE DEVICE ARRANGED TO RECEIVE LIGHT FROM UNSCREENED CELLS TO PROVIDE AN ELECTRICAL SIGNAL CORRESPONDING IN FREQUENCY TO THE FREQUENCY OF INCIDENT LIGHT, REJECTION CIRCUITTS FOR FILTERING OUT COMPONENTS OF SAID SIGNAL AT SAID FIRST AND SECOND FREQUENCIES, AN AMPLIFIER TUNED TO SAID DIFFERENCE FREQUENCY FOR AMPLIFYING THE FILTERED SIGNAL, A SAMPLER COMPRISING AN ELECTRONIC SWITCH OPERATED AT SAID DIFFERENCE FREQUENCY AND ADJUSTABLE IN PHASE FOR SAMPLING THE OUTPUT OF SAID AMPLIFIER AND AN INTEGRATOR FED WITH THE OUTPUT OF THE SAMPLER FOR PROVIDING A SIGNAL OF ONE POLARITY WHEN THE CALL AT A SELECTED LOCATION IS NOT SCREENED AND FOR PROVIDING NO OUTPUT WHEN SAID CELLS IS SCREENED.