Repeater or other unattended equipment can be turned on or off with ordinary telephone Phone at remote station is called and allowed to ring three times Caller then hangs up, waits 20 s, redials number and lets it ring three times again, then hangs up. Circuit then performs desired control function. Any combination of rings can be used as long as
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total is less than nine. Decoder U2 is programmed by moving two jumper wires to various outputs of U2. Relay K2 is chosen to give desired momentary, latching, or stepping function. Relay K1 is used for validating phone line, If remote station keying voltage is taken through contacts of K1, interruption of phone line prevents activation of transmitter. C1 stores voltage during brief interruptions such as when phone is ringing. Article gives detailed explanation of ring-counting circuit. LEDs 11-14 indicate status of control sequence and aid in troubleshooting. K1 and K2 are sensitive DPDT relays with 8000-ohm coils. R11 is selected for desired time setting. -R. C. Heptig, Automatic Telephone Controller for Your Repeater, Ham Radio, Nov. 1974, p 44-48.
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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