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Latching Indicator Driver Disclosure Number: IPCOM000095051D
Original Publication Date: 1965-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 32K

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Related People

Croisier, A: AUTHOR


The latch is for operating a signal lamp by rectified but not regulated AC current.

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Latching Indicator Driver

The latch is for operating a signal lamp by rectified but not regulated AC current.

The current is supplied by AC source 1 and a full-wave rectifier 2. It feeds lamp 3 through a silicon controlled rectifier SCR 4. A circuit comprising diode 5, resistor 6 and capacitor 7 is in parallel with lamp 3. Capacitor 7 is connected through resistors 6 and 8 to the control electrode of SCR 4. Transistor 9, normally cut off, is in parallel with capacitor 7. The latch is controlled through an On input for firing SCR 4. An Off input, fires transistor 9.

When the latch is in the off state, no current passes through SCR 4 and indicator 3. For switching the latch to the on state, there is applied a control pulse to the On input. SCR 4 is fired and capacitor 7 is charged through diode 5. After the control pulse drops, the latch remains in on state, although SCR 4 goes off each time the rectified current reaches zero value. This is because the voltage of capacitor 7 is sufficient for refiring SCR 4 at the next cycle.

For resetting the latch to the off state, an Off input pulse is applied to which fires transistor 9. Capacitor 7 is short circuited and is discharged.


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