When two circuits are physically connected, an oscillation in one circuit will create an oscillation in the other circuit as well. This is *called capacitive coupling*.

Capacitance is the physical connection between the two circuits, and the frequency of an oscillation in a capacitor is determined by the amplitude of the oscillation in its voltage divided by its voltage.

So, if there is a 1 V amplitude of oscillation in one circuit, then there will be a 1 V amplitude of oscillation in the other circuit connected to it. The frequency of this second circuit will be determined by how quickly its capacitance changes from + to – voltage.

Capacitance can either be internal or external. Internal capacitance is inherent to a component, such as a capacitor or inductor. External capacitance comes from components beside each other, such as two parallel plates of a capacitor or two ends of an **inductor facing another component**.

## 2000 Hz

When the top circuit has an oscillation frequency of 1000 Hz, the frequency of the bottom circuit is 2000 Hz. This is because the *bottom circuit must match* the top circuit in frequency.

When one circuit has a higher frequency than the other, they will not operate at the same time. The *lower frequency circuit* will not have enough speed to operate.

So how does this work? How can *two different frequencies* be matched? It all has to do with something called an oscillator. An oscillator is part of a device that produces a constant, repetitive motion or change in some property of a device.

In this case, an oscillator on **one side changes** the voltage level on that side and then transfers that to the other side. The other side then receives this new level of voltage and changes its own level to match it.

This process repeats itself until both sides have reached the same level of voltage and are operating at the same frequency.

## 3000 Hz

In this case, if the top circuit has an oscillation frequency of 1000 Hz, the frequency of the bottom circuit is 3000 Hz.

When you *combine two oscillators* to make a synthesizer, you are actually creating a second oscillator and then combining the frequencies. This is why you can have multiple voices on a synthesizer- there are **multiple oscillators generating frequencies**.

By adjusting the level of *one oscillator compared* to the other, you can *create different sounds*. For example, on a bass sound, you lower the level of the second oscillator and increase the frequency- thus only providing bass frequencies. On a treble sound, you increase the level of the second oscillator to provide more treble frequencies.

## 4000 Hz

In this section, we will discuss how to calculate the frequency of the bottom circuit if the top circuit has an oscillation frequency. As mentioned before, if two circuits are in phase with each other, they will both oscillate at the same frequency.

However, if *one circuit* is 90 degrees out of phase with the other, then the **second circuit** will oscillate at half the frequency of the **first circuit**. You can imagine this by thinking about a clock: 12 o’clock is top-bottom synchronization, whereas 6 o’clock is bottom-top synchronization.

So how do we figure out what the bottom circuit’s frequency will be if the top circuit has an oscillation frequency of 1000 Hz? We use some basic algebra to factor out 1000 and divide by 10000. The answer we get is 0.1, or 1/10 of the original number.

## 5000 Hz

In this section, we will discuss how to calculate the frequency of one circuit in relation to another circuit. Oscillation frequency is calculated by the speed at which a circuit oscillates, or shifts between two points.

There are two types of oscillation frequency: harmonic and sub-harmonic. In this section, we will be *discussing harmonic oscillation frequency*.

When calculating the harmonic oscillation frequency of one circuit in relation to another circuit, you *must first figure* out the total number of cycles each circuit completes in a certain amount of time. Then, you **must divide one number** by the other. The result is the harmonic oscillation frequency of the two circuits.

Let’s return to our example: if the top circuit has an oscillation frequency of 1000 Hz, then the frequency of the bottom circuit is 5000 Hz.

## 6000 Hz

In this article, we discussed how to create a beat sync circuit that can *sync two circuits* with different frequencies. However, in this article, we will discuss how to create a circuit that can change the frequency of a top circuit so that it matches the bottom circuit.

The theory behind this circuit is that if you have a ** top oscillation frequency** and you want to make it the same as the bottom oscillation frequency, you have to double or halve the frequency of the top oscillation frequency.

To do this, you must use a transistor as well as some resistors. The resistor must be of a high value so that there is enough current to travel through the wires. Then, you **must put another resistor** of a low value on either side of the high-value one so that there is enough resistance to match the low value on the bottom circuit.

## 7000 Hz

When the top circuit oscillates at 1000 Hz, the bottom circuit will oscillate at 7000 Hz. This is because the bottom circuit has to match the speed that the **top circuit vibrates** at.

When the top circuit slows down to 900 Hz, the bottom circuit will have to vibrate at 8100 Hz, because its own frequency does not change. The same is true when the **top circuit speeds** up to 1100 Hz; then, the bottom circuit will have to vibrate at 9300 Hz.

The ratio between these frequencies is always 7:10, which can be deduced by **dividing one number** by the other. This constant ratio keeps both circuits in sync with each other.

When using both of these beat-**matching techniques together**, it is important to pay attention to how fast or slow each individual frequency is changing and match those values correctly.

## 8000 Hz

In this blog post, we discussed how to create a beat by **using two different oscillation frequencies**. By having *one oscillation frequency produce* a periodic wave and then mixing it with a second oscillation frequency, you can create a rhythmic beat.

You can see this concept in action with the top and bottom circuits in a microwave. The top circuit has an oscillation frequency of 1000 Hz, which creates a 1 second wave. The bottom circuit has an oscillation frequency of 8000 Hz, which creates a 8 second wave. When these two waves meet, they create a beat of **8 seconds per cycle**.

Because the top circuit has a lower frequency than the bottom circuit, it takes more time to **complete one cycle**. Because of this, time must be added to the higher-frequency bottom circuit so that both circuits meet at the same point in time.

## 9000 Hz

In this blog post, we discussed how to create a beat by *using two oscillators operating* at different frequencies. You can see this concept in action in many situations.

Music is a classic example. When listening to music, you can *hear two separate sounds* that seem to be beating together to make a rhythm. One sound is the bass, which has a lower frequency and takes longer to repeat, and the other is the treble, which has a higher frequency and takes less time to repeat.

Other examples include cars having **two separate engines** (one for the drive train and one for the air conditioner), clocks with two hands (one for the hour hand and one for the second hand), and phones with dual cameras (one for color and one for black and white).

All of these use oscillators of different frequencies to produce different results.