Integrated circuit tone decoders for telephone applications
Manufacturer： ['ti', 'nxp']
# NE567 Product Series: A Comprehensive Introduction
## 1. Overview
The NE567 is a highly versatile and widely used integrated circuit (IC) belonging to the category of tone decoders. It was first introduced by Signetics and has since become a staple in the electronics industry due to its reliability, ease - of - use, and broad range of applications. This product series is designed to detect specific audio frequencies and generate an output signal based on the presence or absence of the target frequency.
## 2. Key Features
### 2.1 Frequency Detection Range
The NE567 can detect frequencies ranging from 0.01 Hz to 500 kHz. This wide frequency range makes it suitable for a variety of applications, from low - frequency audio signals to relatively high - frequency carrier signals used in communication systems.
### 2.2 High Sensitivity
It has a high sensitivity to the input signal, which means it can accurately detect weak signals. This is crucial in applications where the input signal may be attenuated during transmission or where the signal - to - noise ratio is relatively low.
### 2.3 Adjustable Center Frequency
The center frequency of the NE567 can be easily adjusted using external resistors and capacitors. This flexibility allows designers to customize the device for different frequency detection requirements. By changing the values of these external components, the NE567 can be tuned to detect a specific frequency within its operating range.
### 2.4 Output Control
The NE567 has an active - low output pin. When the input signal frequency matches the tuned center frequency within a certain tolerance (the capture range), the output pin goes low. This output can be used to drive other circuits, such as relays, LEDs, or digital logic gates, making it easy to interface with other components in a larger system.
### 2.5 Low Power Consumption
It operates with relatively low power consumption, which is beneficial for battery - powered applications. This feature helps to extend the battery life of portable devices that incorporate the NE567.
## 3. Functional Block Diagram and Working Principle
### 3.1 Block Diagram
The NE567 consists of several key functional blocks, including a voltage - controlled oscillator (VCO), a phase - locked loop (PLL), a comparator, and an output driver.
### 3.2 Working Principle
- **Input Signal**: The input signal is fed into the NE567. This signal can be an audio tone, a modulated carrier wave, or any other periodic signal within the detectable frequency range.
- **VCO and PLL**: The voltage - controlled oscillator generates a reference frequency that is adjusted by external resistors and capacitors. The phase - locked loop compares the phase and frequency of the input signal with the reference frequency generated by the VCO. When the input signal frequency is close to the reference frequency (within the capture range), the PLL locks onto the input signal.
- **Comparator and Output**: Once the PLL is locked, the comparator compares the input signal characteristics with a set of internal thresholds. If the input signal meets the required criteria, the output driver pulls the output pin low. When the input signal frequency deviates from the tuned frequency outside the capture range, the output pin goes high again.
## 4. Applications
### 4.1 Remote Control Systems
In remote control systems, the NE567 can be used to decode the specific frequencies sent by the remote control transmitter. For example, in a simple infrared remote control for a toy, the NE567 can be used to detect the unique frequency patterns corresponding to different commands, such as forward, backward, left, and right.
### 4.2 Audio Signal Processing
It can be used in audio applications to detect specific tones. For instance, in a musical instrument tuner, the