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MK1 is a covert audio surveillance transmitter disguised as a commonly used office and whiteboard marker, the internal transmitter can also be removed in order to function as a discreet standalone audio surveillance device. With compact dimensions of only 13.9mm x 19.4mm, this transmitter offers exceptional covert placement options.  V3TX 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.

Built with precision, the V3TX is populated by 0402 and 0201 SMD components, enabling the use of smaller batteries without compromising performance. While the reduced size affects operational time, this diminutive transmitter still provides an impressive 12 hours of continuous and uninterrupted audio surveillance. Each unit undergoes meticulous soldering under a microscope and rigorous quality testing before packaging.

The V3TX offers versatility and convenience with its 2x gold-plated button cell battery retainers, facilitating quick battery swaps. It features a discreet design without switches or indicator lights, ensuring covert operation. Additionally, 2x Energizer button cell batteries are included with the transmitter.

As a permanent, always-on "hot-microphone," the V3TX commences live transmission of ambient and surrounding audio immediately upon battery insertion, utilizing the Ultra High-Frequency band for uninterrupted signal transmission. In a cluttered urban environment, the V3TX broadcasts audio over a range of 400-500 meters, extending up to 1 kilometer with Line-of-Sight (LOS) transmission, effortlessly penetrating obstacles like concrete, drywall, and dense vegetation. This transmitter operates on 2x 7.9mm Silver Oxide 1.55V Batteries (included), while any 1.55V 7.9mm button cell can serve as a suitable substitute.

Employ the V3TX for discrete acoustic monitoring in areas of interest. We recommend utilizing any handheld UHF receiver capable of tuning into the standard frequency range of 400MHz-434MHz, which is supported by most UHF receivers. For optimal performance, we suggest the Baofeng UV-5R as our recommended handheld receiver. Your transmitter will arrive with its specific Tx/Rx frequency clearly indicated on its back, ensuring seamless compatibility with your chosen receiver.

Power Supply Options

2x 7.9 mm Button Cells (1.55V) 392/384: 12 Hours Of Continuous Operation.

Dimensions 13.9mm X 19.4mm

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 5g
Output (RF) power   20mW
Antenna Alpha Wire 8 in. Micro Coaxial Cable 38 AWG 
Frequency Range

433 MHz-436 MHz, 2.5 kHz step.

Effective Range 15m From Centre. 
Stability  Highly Stable. Crystal Referenced Phase-Locked Loop.
Crystal 00k/ASK Data Transmitter.

In order to maintain their longevity, transmitters are potted with a compound that seals all onboard components, only the microphone and the battery terminal 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.