Air Transparency Monitor, Xenon Flash Transmitter  -  This is the matching transmitter for the above receiver. The transmitter launches powerful 1000-watt light pulses that last about 20 microseconds . . . [Circuit by Dave Johnson P.E.,  06/17/00]

Audio Amp + 3Khz Filter  -  This circuit is the audio amp section for a complete optical transmitter.  The circuit amplifies and filters the voice audio signals from an electret microphone.  The circuit is described in more detail in . . . [Circuit by Dave Johnson P.E.,  06/04/00]

Inductive Pulse Receiver (175Khz)  -  This circuit is discussed in more detail in the Experimenters Journal. The receiver’s six inch diameter coil detects the ring signal from the above transmitter and use a single NPN transistor to provided enough amplification for the signal to be easily viewed on an oscilloscope . . . [Hobby Circuit designed by David Johnson P.E.,  06/27/00]

Line Powered Xenon Flash Transmitter  -  This line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . [Hobby Circuit designed by David Johnson P.E.,  06/09/00]

Line-Powered Xenon Flash Transmitter  -  This line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . [Circuit by David A. Johnson P.E.,  06/03/00]

Locate a Plastic Pipe  -  I used this circuit once to track down the location of a plastic pipe, buried underground.  It transmits a weak RF signal, which can be picked up by a portable AM radio from about 6 feet away . . . [Hobby Circuit designed by Dave Johnson P.E.,  12/14/04]

Plastic Pipe Finder  -  I used this circuit once to track down the location of a plastic pipe, buried underground.  It transmits a weak RF signal, which can be picked up by a portable AM radio from about 6 feet away . . . [Circuit by Dave Johnson P.E.,  12/14/04]

Xenon Flash Transmitter  -  This line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/09/00]

Xenon Flash Transmitter-Air Transparency Monitor  -  This is the matching transmitter for the above receiver. The transmitter launches powerful 1000-watt light pulses that last about 20 microseconds . . . [Hobby Circuit designed by David Johnson P.E.,  06/17/00]