This is the circuit that sparked off all the other Link Telephone Intercom designs. Originally designed back in 1996 with heavy duty relays and their contact banks, it was updated late last year with the addition of IC1 in place of a simpler transistor multivibrator, the replacement of all relays and contact banks with optocouplers, and the additi
Click here to download the full size of the above Circuit.
on of the two transformers as part of the transmission bridge (see explanation below) which was comprised partly of the relay coils. If you just want simple ‘no frills ’ communication from one phone to another, then this is the right circuit for you! This version is much more compact, more economic on power drain (yes, you can run it off of batteries – eg: a 12 volt Gel Cell!) and has no moving parts, except for the switch hooks inside each of the phone handsets. This was one of the earliest Link designs. It works by either caller simply picking up their handset and ‘buzzing ’ the other phone. There are no numbers to dial (in fact, no dial tone either – just ring tone, which pulses on and off in unison with the buzzer at either end when a call is in progress. ) Let ’s assume that #1 picks up their handset. This forms a DC loop between the handset, the 1k winding of Tx1, the 0v_ earth terminal, the +12 volts terminal and the leds inside OC1 and OC3. IC1 (an NE556 dual timer chip) is always ‘on ’ –that is, it ’s always pulsing on and off at output pin 9, which then drives the second half of the timer chip on and off via D1 to pin 4, producing ring pulses, and ring tone from pin 5 via C3 and C4 to the 8R windings of Tx1 and Tx2. The transistor inside OC1 switches on hard, taking its collector lead low, and ring pulses are fed from pin 9 of IC1 via R5 and Q1, to the emitter of OC1, through to its collector lead, and then on 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: