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Telephone Headgear: A compact, inexpensive and low component count telecom headset can be constructed using two readily
available transistors and a few other electronic components. Since the circuit draws very little current, it is ideal for parallel operation with electronic Telephone set. FAIR WARNING -THIS
SITE HAS ANNOYING POP UP ADS. (added 4/02) |
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Telephone in Use Indicator #2: (electronic Circuit / Schematic added 10/04) |
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Telephone in Use Indicator: With this circuit mounted in or near every phone in the house, it will allow users to know if
the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This will cause the FET (2N4360)
to turn on and also turn on the transistor (2N2222). When the transistor turns on it will allow current to flow through the LED and make it light. A blinking LED could be used to make the
effect better. (added 6/06) |
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Telephone in Use LED Indicator: (electronic circuit added 7/03) |
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Telephone in Use Light: (electronic circuit added 7/03) |
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Telephone In-Use Indicator (circuitsdb): See image above Copyright 2006: Bill Bowden
[url]http://ourworld.compuserve.com/homepages/Bill_Bowden/[/url].... (added 2/07) |
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Telephone In-Use LED Indicator: (electronic circuit added 4/05) |
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Three Level Audio Power Indicator #2: Battery-operated Three LED display that connect it to loudspeaker
output (added 6/06) |
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Three Level Audio Power Indicator: Battery-operated Three LED display that connect it to loudspeaker output (added 9/04) |
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Triple-Supply Power-Good Indication with the ADM108x: AN-726 Analog Devices Application Note (app note added
6/06) |
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Ultra Low Power LCD Indicator: This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It
also has the advantage of being easy to read in full daylight. With the parts shown, it is possible to display four bits of information. The display that I used has three digits and 2 decimal
points for a total of 23 segments. Different groupings of segments can be.... (added 16/06) |
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Water Level Alarm: (electronic design added 9/02) |
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Water Level Controller: (electronic Circuit / Schematic added 10/04) |
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Water Level Indicator with Alarm: Here is a simple, versatile circuit which indicates the level of water in a tank. This
circuit produces alarm when water level is below the lowest level L1 and also when water just touches the highest level L12. The circuit is .... (added 10/04) |
