This circuit is used to give `1` signal when the phone is ringing. As you can see the ct. is directly connected to the phone line. The 4.7 uF blocks the DC loading on the phone line. This means that there is voltage on the 10K resistance only when the phone is ringing. This voltage is of course alternating, and it is half wave rectified by the diode, so that, only the positive spikes charge the capacitor. So the net result is that the capacitor is charged only when the phone line is ringing. The variable resistor is used to absorb the `silence` period during the ringing so that the voltage stays at logic high. By adjusting this variable resistance, you can prolong or shorten the time period after which the capacitor voltage will turn to logic low. This period should be adjusted to be about 4 seconds.
Click here to download the full size of the above Circuit.
Click here to download the full size of the above Image.
In fact, is not important and can be entirely omitted from the circuit, it is simply a 4 bit counter that its clear is used to give "1" signal from the anding of the " 4 "o/p bits, but it's importance rises when the ck used is very slow that's when ring 1/0 gives "1" signal, this latch "1" gives instantaneous "1" signal which exhibits "1" signal at o/p , that's we donut have to wait for the ck to get "1" signal from latch 2. 1-Prevent "1" signal at o/p when there is a coming call.
2-Making o/p signal when I make a call.
This is done using a delay flip-flop ,and a logic ct. which controls two things, the o/p signal and the ck of the delay flip-flop, as in the design , when phone rings ,ring1/0 gives "1" signal, so "D" pin now have "1" signal on it before raising the hang, ring1/0 gives "1" signal, and also hang 1/0 gives 0 SIGNAL.
After raising the hang to answer the phone ,we have : "1" signal from ring1/0 as the capacitor has not yet discharged, and "1" signal from hang1/0 after we raised the hang, so this means that is the ck is enabled on the delay f.f , but when the capacitor discharges, ring1/0 gives now "0" signal ,this means that the expected thing here is to have o/p signal as the hang is still raised , but the design exhibits the ck at this instance on the delay f.f , making its "q" pin high as long as the hang is raised ,when the call is finished and the hang is off, this enables the ck and we go back to...
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.....
characters left: