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Phone in use indicator 1 - Use a CMOS 4049 Hex Interter because (supposedly) has
high drive output. And since it's CMOS, it can operate with Vcc from +3 to +15V. And
it has a high input impedence.
.(electronic schematic added 06/09) |
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Phone in use indicator 2 - LED will start blinking if a phone is in use.
.(design
added 06/09) |
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Phone in use indicator 3 -
.(design added 06/09) |
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Phone in use indicator 4 - The circuit I built gives a visual indication at each
extension when any extension is off-hook. It is line-powered, and the maximum number
that can be used on our system is three. Since they all draw power at the same time to
light the LEDs, any more indicators would cause an off-hook condition. Some changes
could be made to reduce the current draw, to allow using more indicators, but the
brightness of each led would suffer. The LEDs I used are tiny, but
.(design added
06/09) |
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Phone in use indicator 5 -
.(electronic schematic added 06/09) |
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Phone in use indicator 6 - R1 and R2 form a voltage divider, insuring that the
phone line sees a high impedance load and that high voltages (such as the ring
voltage) are easily dissipated by the protective diodes (CR1 and CR2). Also
(obviously) they serve to divide all incoming voltages by two. Capacitor C1 filters
out some of the audio signals that might otherwise make the LED flicker with
speech.
.(electronic schematic added 06/09) |
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Phone In-Use Light-manual - ASCII format (circuit design added 10/06) jun 21, 2006 |
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Phone Light Flasher (Aaron Cake) - when the ph1-rings, lights connected to circuit
flash (added 04/03/02) |
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Phone Line to Audio - ASCII format (circuit / design added 8/03) |
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Phone Off Hook Indicator - ASCII format (electronic circuit added 7/03) |
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Phone Rang' Indicator Light - ASCII format (electronic circuit added 7/03) |
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Power Amplifier Clipping Indicator - (schematic / circuit design added 9/02) |
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Power Loss Indicator - Dave Campbell designed this clever circuit. It uses
two neon lamps to indicate if power to a 120vac appliance had been interrupted.
(added 12/04)
.(designed by David A. Johnson) |
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Quiz Show Indicator - ASCII format (added 4/05) |
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Rainbow LED indicates voltage With color - 12/07/04 EDN-Design Ideas: Meters that
indicate analog levels via a moving-pointer meter, a numeric display, or a column of
LEDs typically occupy considerable panel area and require more than a casual glance to
read. An indicator lamp or LED takes little space but indicates only an on or off
condition. However, an unobtrusive LED that changes color as a function of a measured
value would enable an observer to easily asse.....(design idea added 1/05) |
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Remote Doorbell Indicator - (electronic design added 9/02) |
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Remote Doorbell Warning Switch - This circuit should only be used with the
solenoid type chime doorbells, the electronic type that play tunes will not work here.
The hardest part for this circuit was the title. It is quite easy to miss the sound of
a doorbell if you are watching TV , this circuit gets round the problem by providing a
visual indication, i.e. a lamp....(added 2/06) |
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Remote LED Indicator Light - There are times when you would like to transmit a
signal from one LED indicator light to second LED at another location. The
circuit below works well for this application. It takes advantage of the fact
that the internal infrared LED inside an opto-isolator has a lower voltage drop than
the visible LED being tapped into. Using a darlington type opto-isolator also
means very little current needs to be diverted to the isolator.....
.(designed by
David A. Johnson) |
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Ringing Phone Light Flasher (Aaron Cake) - when the ph1-rings, lights connected to
circuit flash (added 04/03/02) |
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RS232 Data Bus Status Indicator - This circuit indicates TXD and RXD activity.
The thresholds are set at plus 3 volts and minus 3 volts. (added 12/04)
.(designed by
David A. Johnson) |
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Simple blown fuse indicator sounds an alarm - 07/10/08 EDN-Design Ideas: A simple
blown-fuse-indicator circuit sounds a buzzer and flashes an LED when a fuse
blows.....(design idea added 009/08) |
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Simple Circuit Detects Current Pulses - 01/06/94 EDN-Design Ideas: The pulse
detector provides a visible indication of positive and negative current pulses. The
pulses amplitudes can vary from20 to150 mA. The pulses durations can range from10 to40
msec, and their repetition rate can span40 to180 pulses/minute.....(design idea added
3/03) |
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Simple Circuit Forms Peak/Clipping Indicator - 11/22/01 EDN-Design Ideas: The
simple peak detector in Figure 1 is the result of a need for a single-5V-supply,
level/clipping indicator for a multimedia-PC sound system. The design is unique in
that it detects both stereo channels on a single peak-hold capacitor. All the
adjustments in the circuit simultaneously apply to both left and right stereo
inputs.....(design idea added 1/05) |
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Single LED Indicates Two Power States - 12/05/96 EDN-Design Ideas:
-Uses a single bicolor LED to indicate both power-on and blown-fuse
conditions.....(design idea added 3/03) |
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Stabilised Power Supply with Short-Circuit Indication - (electronic Circuit /
Schematic added 10/04) |
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Status Indicator Flags Five Discharge States - 01/20/94 EDN-Design Ideas: The
circuit actually indicates five conditions of the battery. A steady glow assures the
user that the battery is strong and healthy. A2-Hz brief flicker off indicates that
the battery is starting to show age. A more insistent,50%,5-Hz flashing is a warning
to have a spare battery on hand. A brief flicker.....(design idea added 3/03) |
