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For those in search of extended operating times with a compact transmitter, we present our L2TX Audio Surveillance Transmitter, designed to meet your needs. When paired with a CR123A Li-ion battery, this transmitter offers an impressive broadcasting duration of 7 days, This transmitter is now available with a new extremely sensitive KNOWLES microphone, and a new high-powered crystal generating 20mW of RF power, ensuring superior frequency stability and delivering enhanced audio sensitivity. For custom power options to extend the operating time, please feel free to contact us for further assistance.

We carefully selected the CR123A battery due to its availability in both alkaline and rechargeable Li-ion variants, as well as its compact size. This battery provides ample capacity and can be easily obtained from hardware stores and pharmacies. With a nominal voltage ranging from 3.2V to 3.7V and a capacity between 1500mAh and 1550mAh, this battery ensures excellent range and audio pickup performance.

This transmitter operates as a permanent, always-on "hot-microphone," immediately initiating live transmission of ambient and surrounding audio once the battery is inserted. It operates seamlessly on the Ultra High-Frequency band, ensuring uninterrupted signal transmission.

The L2TX boasts an impressive broadcasting range of 700 meters in a cluttered urban environment and extends up to 1.2 kilometers with Line-of-Sight (LOS) transmission. It effectively penetrates obstacles such as concrete, drywall, and thick vegetation, delivering reliable audio transmission to any UHF receiver. The transmitter operates efficiently on a single CR123/A Li-ion cell.

Utilize the L2TX for remote listening in areas that require discreet acoustic monitoring. We recommend using any handheld UHF receiver capable of tuning into the standard frequency range of 400MHz-700MHz, as this range is supported by most UHF receivers. Our recommended handheld receiver is the Baofeng UV-5R. L2TX will arrive with its specific Tx/Rx frequency clearly indicated on its back.

Power Supply Options

1x CR123A (3v) : 7 + Days of continuous operation depending on mAh.


CUI: 100 Hz ~ 20 kHz Analog Microphone Electret Condenser Omnidirectional (-42dB ±3dB @ 94dB SPL)

KNOWLES BJ-21590: 300 Hz ~ 5 kHz Analog Microphone Magnetic Omnidirectional (-75.5dB ±3dB @ 74dB SPL)

Weight 12g
Output (RF) power  20mW
Antenna Alpha Wire 8 in. Micro Coaxial Cable 38 AWG 
Frequency Range

433MHz-436 MHz, 2.5 kHz step.

Effective Range 15m From Centre. 
Stability  Highly Stable. Crystal Referenced Phase-Locked Loop.

00k/ASK Data Transmitter.

In order to maintain its longevity, the L2TX is potted with a compound that seals all onboard components, only the microphone and the battery terminal pads are accessible and made visible.

We can design for your needs. TINYTX has designed and manufactured hidden and covertly disguised audio surveillance transmitters for several client projects and applications. Contact us for turnkey solutions.