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Remote operated musical bell using UM3481

This article is about remote operated musical bell using UM3481. The M348X series IC is a mask-ROM-programmed multi melody generator , implemented by CMOS technology. It is designed to play the melody according to the previously programmed information and is capable of generating 16 songs with 3 instrument effects : piano, organ and mandolin. The device also includes a pre-amplifier which…

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Test UM3481 musical circuit

The M348X series IC is a mask-ROM-programmed multi melody generator , implemented by CMOS technology.It is designed to play the melody according to the previously programmed information and is capable of generating 16 songs with 3 instrument effects : piano, organ and mandolin. The device also includes a pre-amplifier which provides a simple interface to  the driver circuit. The M3481…

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Telephone misuse indicator

When the phone line is in idle condition (on hook), the full voltage of 48V DC from the exchange appears across the line. When the phone is engaged by lifting the hand set, the voltage across the line falls down to around 12V. Thus, under idle condition (48V), VR1 is adjusted to give a positive biasing voltage to the base of Q3. As Q3 conducts Q1 gets into reverse bias and stops conduction. If the phone is engaged, Q3 stops conducting due to voltage drop across the lines, and subsequently, Q1 and Q2 starts oscillating and beeping is heard. Thus, this circuit can be used as an indicator for telephone tapping and misuse by an unauthorized person.

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OR-gate realization

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator.
As we block the light falling on LDR, the calculator starts counting.
For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys.

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Object counter using LDR and calculator

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator.
As we block the light falling on LDR, the calculator starts counting.
For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys.

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Water Level Indicator

We can use the logic of making an automatic light detector to make a simple water level indicator.We just need to remove LDR from the circuit and put the wires into water, then it simply works as water level indicator. There is a specific resistance between the wires that are dipped into water and conduction of electricity through water gives biasing voltage to base of transistor.

The sensitivity can be adjusted using VR1. Put 470K variable resistance in VR1.

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