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Dielectric Sensing of Punched Holes

IP.com Disclosure Number: IPCOM000094104D
Original Publication Date: 1966-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

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This device detects the presence of punched data in a card or paper tape.

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Dielectric Sensing of Punched Holes

This device detects the presence of punched data in a card or paper tape.

The device comprises an insulated gate field effect transistor 10 which is used as load for a tuned circuit. In this arrangement, the resistive and capacitive loading effects on the tuned circuit are at an extreme minimum. Oscillator 12 drives a plurality of resistors R1... Rn which are connected to high Q tuned circuits. In a device for reading record card data on a column-by-column basis, twelve resistor tuned circuit branches are required. The tuned circuit comprises coil 14 and parallel capacitors C16 and C18. The latter is adjusted so that the tuned circuit is at the antiresonant point without a card interposed between the plates of C16. The presence of a card between the plates of C16 detunes the circuit and its output falls off. The values of the resistors R1...Rn are chosen large compared to the detuned impedance and comparable to the tuned impedance of the tuned circuit. If C18 is approximately equal to 100 times the value of C16, it is necessary for the tuned circuit to have high Q values. If the frequency of the system is high, a detectable change in output suitable for card reading is obtained at terminal 20.


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