Phone In-Use Light-manual -  ASCII formatjun 21, 2006. . . 

Phone Light Flasher -  when the ph1-rings, lights connected to circuit flash. . .  [Design by Aaron Cake]

Phone Line In-Use Indicators -  Presented are two different designs that perform the same function. Each circuit lights an LED when a telephone line is in use, and can be placed at extension telephones to alert others not to interrupt. Unlike "off-hook" indicator circuits, these circuits do not have to be inserted in series with the telephone; they are simply plugged into the telephone line to provide an indication that one or more of the phones on that line are being used. Both circuits are powered by 9v batteries, and therefore present little danger of imposing an unsafe condition on the telephone line or equipment. . . .  [Designed by Arthur Harrison]

Phone line status indicator -  Scroll to find this one. This circuit has been designed by Gabriele Bandini. His home is full of telephones, modems, and. . . kids. After a dozen of modem crashes, he decided to put an indicator LED on every phone plug to show to the family when the phone line is free. . . .  [Alberto Ricci Bitti]

Phone Line to Audio -  ASCII format. . . 

Phone Off Hook Indicator -  ASCII format . . . 

Phone Rang' Indicator Light -  ASCII format . . . 

Piezoelectric Water Flowing Indicator -  The vibrations associated with water flowing through a pipe are picked up by an inexpensive piezo wafer. The signal from the wafer is first boosted by a micropower transistor Amplifier and then fed to an ultra low power voltage comparator . . . [Hobby Circuit designed by David Johnson P.E.,  07/26/09]

Power Amplifier Clipping Indicator -  At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty". If this happens too often or is too severe, tweeters are the first to go - they are damaged by the excessive power generated by a combination of "power compression" and the harmonics created when an Amplifier clips. The same may well happen to one's ears, but the effect is much more subtle (and cannot be fixed !). . . .  [Design by Rod Elliott - ESP]

Power Indicator for the Water Softener -  This power indicator circuit is intended to be used as an extension for the water softener. It might be easier to just place a LED but it is better to make a rectifier that detects the presence of the 15 kHz signal generated by the 555 IC. Water Softener Power Indicator Schematic The rectifier is connected at the water. . .  [Circuit posted by Popescu Marian]

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. . . .  [designed by Dave Campbell, Boulder CO]

Programmable LED Indicator -  This circuit uses CD4017 to program a bicolour LED in ten different modes with combinations of red and green. . . .  [© EFY Enterprises Pvt. Ltd. All rights reserved.]

Quadruple Infrared Proximity Detectors Circuit -  The circuits on this page are for an Infrared - Proximity Detector using the Vishay Electronics - TSOP4830 "IR Receiver Modules for Remote Control Systems"Scroll down to find this one. . . .  [from Rob Paisley's Model Train web site]

Quiz Show Indicator -  ASCII format. . . 

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