ISD1820 is a single-chip voice message recording IC for single message recording and playback. It allows to record 10 sec of audio and play it back under microcontroller or by manual mode. As it consists of an inbuilt microcontroller, a message up to 10 sec long can be recorded. By connecting a resistor, these 10 secs can be extended to 20 sec. It is a non-volatile module, hence can be recorded up to 100000 times and can be stored without power. The small inbuilt audio amplifier in the module drives an 8-ohm speaker directly.
ISD1820 chip designed as a resistor-controlled oscillator input (ROSC) in which sampling rate and maximum duration of audio can be controlled by placing a resistor between ROSC pin and GND, this sets oscillator frequency. The audio play volume of this module increased by adding AGC input to the LED output pin. These modules operate directly by push button or with every microcontroller. Specialized analog flash memory used to store messages, even when power removed. In this module, it is also possible to record at one rate and playback at another. Thus it will serve to speed up or slow down the playback which might be useful for creating sound effects. For this, a pot used to wired in the module.
The power output of this module is sufficient to drive a small speaker. Or the output used to drive the input of an audio amplifier if louder sound required. In addition, Header pins provided for easy interface to a microcontroller and playback controlled with just one digital pin.