ELECTRONIC TEACHING AID

• US 3,763,577 A
• Filed: 01/26/1972
• Issued: 10/09/1973
• Est. Priority Date: 01/26/1972
• Status: Expired due to Term

• Current Assignee: David R. Goodson
• Original Assignee: David R. Goodson
• Inventors: Goodson, David R.
• Primary Examiner(s): Michell, Robert W.
• Assistant Examiner(s): Wolff, J. H.
• Application Number:
  US05/220,742
• Time in Patent Office: 622 Days
• Field of Search: 35/9R,9B,48R
• US Class Current: 434/352
• CPC Class Codes: G09B 5/06 with both visual and audible presentation of the material to be studied

Abstract

A portable teaching aid for school use which determines first student response to questions asked by the teacher by having the students depress electrical switches. The signal from the first switch depressed is fed into a control console containing a latching, exclusive or-gate. The gate lights a lamp on the control panel corresponding to the switch depressed and prevents any further responses after the first response from being indicated. A bell may be provided to ring with the first response. The circuit used does not need the conventional crosscircuiting using transistors and diodes to achieve the exclusiveor function. Silicon controlled rectifiers (SCR'"'"''"'"'s) share a common-cathode resistor which produces a threshold voltage when any one SCR is triggered into conduction. This voltage raises the firing threshold of the non-conducting SCR'"'"''"'"'s above the available trigger voltage producing the exclusive-or (lock-out) condition.

Claims

1. In an educational device for determining, latching and visually displaying the first response of a group of quiz contestants the improvement comprising:

a. a two wire input power source, b. a plurality of silicon controlled rectifiers each having an anode, a cathode and a gate lead, c. a corresponding plurality of gate resistors, d. wiring means connecting the common input line of said power source to one end of all of said gate resistors, e. wiring means connecting the other end of each of said gate resistors to the gate lead of its corresponding silicon controlled rectifier, f. wiring means connecting the anodes of each of said silicon controlled rectifiers to one terminal of a two terminal signal light, the other terminal of the two terminal signal light being connected to the positive input line of said power source, g. wiring means connecting the cathodes of each of said silicon controlled rectifiers to a threshold voltage line, said threshold line having a positive voltage determined by the combined voltage drop of the signal lamp and its associated silicon controlled rectifier so that the resultant threshold voltage is sufficient to set up a trigger voltage and activate the gate of a silicon controlled rectifier in a cooperating bell circuit, h. a voltage divider connected between said positive and common input lines for generating an intermediate trigger voltage output, i. a corresponding number of normally open single pole single throw switches, each switch being connected by wiring means between the said trigger voltage output and the corresponding one of the other ends of each of said gate resistors with each said switch being actuatable by a contestant to indicate his response, j. a corresponding number of diodes connected by wiring means between said trigger voltage output and the corresponding one of the other ends of each of said gate resistor, respectively, so as to isolate the positive voltage at the gate of a triggered silicon controlled recifier from all other gates, k. a gate voltage threshold setting resistor having one end connected to said common input line and the other end connected to the threshold voltage line, said gate voltage threshold resistor further being connected to a bell circuit, whereby closure of any of said switches causes substantially immediate firing of the cooperating silicon controlled rectifier, causes the appropriate signal lamp to glow and produces a positive voltage at the cathodes of all silicon controlled rectifier through the threshold setting resistor effective to raise the firing voltage threshold of all remaining silicon controlled rectifiers so they cannot be triggered into conduction and also actuates the bell circuit.

2. The circuit of claim 1 wherein said gate voltage threshold resistor is lowered in value whereby a predetermined plurality of responses is indicated without regard to priority within the group.

3. The circuit of claim 1 wherein said trigger voltage source comprises two resistors arranged as a voltage divider with one side of one resistor connected to the positive line and the other side connected to any of said gate resistors.

4. The circuit of claim 3 wherein the voltage produced by the divider when 2 or more gate resistors are connected in parallel through the simultaneous closing of said switches is below the firing threshold of any silicon controlled rectifier.

5. The circuit of claim 1 comprising in addition capacitors across said gate resistors effective to cancel spurious noise pulses.