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Voice switch saves space in two-way talk apps

Posted: 21 Oct 2009 ?? ?Print Version ?Bookmark and Share

Keywords:voice switch? power amplifier? two-way conversation device?

NJW1128 voice switch

New Japan Radio Co. Ltd brings to the market, the NJW1128 voice switch with power amplifier designed for two-way conversation devices such as door intercom, interphone, hot-water supply system remote controller with call function and conference systems.

In March 2008, New Japan Radio released the NJW1124 that integrated the functions required for two-way conversation devices in one chip. However, it still needed an external power amplifier. Now the company has unveiled the NJW1128 that already integrates this power amplifier, for truly integrated two-way conversation devices. Furthermore, the fact that an external power amplifier is no longer needed cuts PCB space substantially.

The NJW 1128 consists of a power amplifier, receiver amplifier, line amplifier, microphone amplifier, sending/receiving attenuator, level detector and noise detection circuit (background noise monitor). In two-way conversation devices that have a speaker and a microphone close to each other, sound from the speaker is picked up and amplified by the microphone and then reproduced by the speaker, causing howling and echo. The NJW1128 prevents these problems by determining which side has priority based on the volume of the input signal. It increases the volume on the sender's side and decreases the volume of the receiver. Plus, the noise detection circuit detects and reduces surrounding noise to keep conversation clear.

Unlike conventional voice switches that require an electrolytic capacitor, the NJW1128 is compatible with ceramic condensers, improving reliability, lowering cost and extending operating life.

It has two important functions inside that are realized by discrete circuits conventionally, one is press-to-talk function, and the other is mode monitoring port.

The NJW1128 features operating voltage of 3.9V to 5.5V, a forced sending/receiving terminal and a mode monitoring port. The attenuator gain range between transmit and receive is 52dB. The microphone-amplifier has mute function, and each path has a background noise monitor. It offers four-point signal sensing and chip disable function or power save. The microphone and receive amplifiers are pinned out for flexibility. It comes in a 9mm x 9mm x 1.5mm typ LQFP-48-R3 package.

The NJW1128 voice switch is priced at $3.32/unit.

For application notes on voice switches click here.

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