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Description
em-trak B921 Class B AIS Transceiver - 2W CSTDMAB921 Class B AIS Transceiver 2W CSTDMA **As the FCC requires all units sold in the US to be programmed by a qualified technician. Please submit the form below for programming at the time of purchase. A copy of the MMSI registration or FCC Ship Station License is required along with the vessel master or owner's signature on the completed programming form.** Click here to download form. The B921 is a 2W CSTDMA Class B AIS transceiver, delivering em
B921 Class B AIS Transceiver - 2W CSTDMA
**As the FCC requires all units sold in the US to be programmed by a qualified technician. Please submit the form below for programming at the time of purchase. A copy of the MMSI registration or FCC Ship Station License is required along with the vessel master or owner's signature on the completed programming form.**
The B921 is a 2W CSTDMA Class B AIS transceiver, delivering em-trak's advanced performance and reliability through next-gen technology. Small and durable, this trusted transceiver processes all AIS transmissions in real-time, even at the range limit, so you always have the complete picture and the time to respond.
em-trak's intelligent connectivity means the B921 can be connected to any chart-plotter and comes equipped with integrated GPS technology and best-in-class, ultra-low power consumption. Installation is also simplified with our unique FLEXI-FIT® bracket system to have you up and running in no time at all.
Features:
- Certified AIS Class B – 2W CSTDMA
- Global certification - USCG / FCC / Canada / Europe
- SRT-AIS™ Transceiver Engine for superlative proven performance
- FLEXI-FIT™ bracket system for easy, convenient, and secure installation
- Internal high-performance GPS receiver and antenna (external antenna optional)
- Water, pressure spray, and damp proof (IPx6, IPx7 certified)
- Protected from vibration, shock, and extreme temperatures
- Small and lightweight
- Ultra-low power consumption – best in class
- NMEA 0183 & NMEA 2000
- Automated health and performance monitoring
- Silent mode (transmit-off) function
- Enhanced RF screening to protect against electromagnetic interference
- Built-in power surge protection
Physical & Environmental Specifications:
- Size (H x W x D): 150 x 115 x 45mm
- Weight: 375kg
- Operating temperature: -25°C to +55°C
- Storage temperature: -25°C to +70°C
- Ingress protection: IPx6 and IPx7
Electrical Specifications:
- Supply voltage: 12V or 24V DC
- Supply voltage range: 9.6V - 31.2V DC
- Average current (at 12V): 135mA
- Peak current: 2A
- Average power consumption (at 12V): 1.6W
- Galvanic isolation: NMEA 0183, NMEA 2000, VHF antenna port
Connectors:
- VHF antenna: SO-239
- GNSS: TNC
- Power: 12-way circular multipole
- NMEA 2000: 5-way Micro-C connector
- USB: USB Micro-B
Data Interfaces:
- NMEA 0183: 2 x bi-directional ports
- NMEA 2000: NMEA 2000 Ed 3.101, LEN=1
- USB: PC virtual com port for NMEA 0183 data
Standards Compliance:
- AIS standards: IEC 62287-1 Ed. 3, ITU-R M.1371.5
- Product safety standards: EN60950-1 2006 +A11:2009 +A1:2010 +A12:2011 +A2:2013 EN62311:2008
- Environmental standards: IEC 60945 Ed. 4
- Serial data interface standards: IEC 61162-1 Ed 5.0, IEC 61162-2 Ed 1.0
- NMEA 2000: NMEA 2000 Ed 3.101
- GNSS performance standards: IEC 61108-1 Ed 2.0, IEC 61108-02 Ed 1.0
GNSS:
- Systems supported: GPS, GLONASS, BeiDou, Galileo (two of any combination, three including GPS, Galileo)
- Channels: 72
- Internal/external antenna: Internal or optional external antenna
- Time to first fix from the cold start: 26s
VHF Transceiver:
- VDL access scheme: CSTDMA
- Operating frequency: 156.025MHz - 162.025MHz
- Channel bandwidth: 25kHz
- Receivers/transmitters: 2 x receivers, 1 x transmitter
- AIS receiver sensitivity (20% PER): -111dBm
- AIS transmitter power: 2W (+33dBm)
User Interface:
- Indicators: Power, transmit timeout, error, silent mode
In the Box:
- 1 x AIS transceiver
- 1 x Power and data cable (2M)
- 1 x FLEXI-FIT™ mounting bracket
- Complete with screws & optional fixing tape
Manufacturer : em-trak
Manufacturer Part No : 430-0001
UPC : 672975210502
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.6 ★★★★★
Based on 26 reviews
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Product Reviews
★★★★★ 5
Very good speakers
Size: Pair
The r51ms are used to compliment my klipsch rp500m speakers and a 12 inch subwoofer in a large living room. By placing the r51m speakers to the outside walls , and the rp500m speakers to the interior, closer to the amplifier, and with the subwoofer set on deep bass only at just enough volume to barely compliment the sound, the large living room is more than sufficiently covered with at least true high fi quality sound, if not true budget audiophile sound. My entire 2.1 system is all klipsch. That's how I want it.
I am using them with a high powered tube amplifier, so presence and clarity is awesome. Placement is critical. I was initially disappointed until I switched the r51ms to the spread to the outside walls position, and the rp500ms to the interior, closer to the amplifier. The difference was remarkable. The 2 different klipsch speakers, ie one a rp and the other a r series blend together perfectly with no clash whatsoever because of somewhat more refined sound on the rp500m speakers. The rp500m speakers do sound higher end , but they are supposed to, but with the speakers as outer r51m and inner rp500m, and the klipsch subwoofer at deep bass with just a touch of volume the result is sound of such quality that I can honestly say I can be content and satisfied with it. I can say my system is complete, and no further improvement, upgrades are needed. Tower speakers as primaries are not necessary because of the high quality of sound and the high sensitivity of the 4 klipsch bookshelf speakers and klipsch subwoofer. This saves me money during this rapid inflation period of time. I could easily say that what I have sounds more than good enough to be satisfied and content with without any desire to upgrade further at this point.
Shipping speed was excellent via Amazon itself, and the box and speakers arrived in handled with care and new condition.
I am not disappointed at all now that the r51m speakers are the outside speakers, spread apart from corner wall to wall to compliment the interior placements of my rp500m speakers by klipsch. Im all klipsch here and I love it. 5 stars categorically. As previously stated, I see no need for primary tower speakers, even in a large living room, and that equals high quality sound and savings of money at the same time. I recommend these speakers. They do more than just do sound quality wise.
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Reviewed in the United States on August 22, 2025
★★★★★ 5
Awesome speakers.
Size: Pair
Love Klipsh speakers. Beautiful, full, rich, clear sound. Combine with a sub for best sound. Very loud. Love these.
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Reviewed in the United States on April 30, 2026
★★★★★ 5
Love it
Size: Pair
These are nice for any audiophile. They look and sound amazing.
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Reviewed in the United States on May 14, 2026
★★★★★ 5
Great Sound
Size: Pair
Great things sometimes come in little packages. Powerhouse sound with virtually no input at all. Tight, crisp, and well-made as usual from Klipsch. If you are looking for a powerhouse monitor these are what you want.
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Reviewed in the United States on April 22, 2026
★★★★★ 4
Great starter speakers - for the right price.
Size: Pair
A good all-around pair of starter speakers if you're planning on using them as standalones. These will have zero trouble filling a small to medium sized space with rich and detailed sound at low to mid volumes. The bass is adequate for their size. They're not going to knock your socks off on more thumpy genres. I would imagine pairing them with a subwoofer would make quite the difference but for rock and some synth pop, they're pretty sweet. Plus the copper woofers look very striking without the faceplates.
That said, I say these are best suited at low to mid volumes because cranked, the higher frequencies can be awfully fatiguing coming out of these speakers. I would not pay anywhere close to the $349 MSRP for these (you can probably find a pair of far superior RP-600Ms for around that price nowadays). Around $150 seems like a sweet spot for the R-51Ms, but the Sony SSCS5s and Fluance Signature bookshelfs are very comparable, if not better sounding for around the same price. Still, these will probably more than satisfactory if you're not expecting to be blown away by them.
UPDATE 5/20/25:
Can confirm that the subwoofer made a big difference. I was going to retire these since I replaced them with some bigger floor speakers on my main setup but I decided to try them out in place of the factory speakers on the Klipsch ProMedia 2.1 I have hooked up to my computer. Not only does the onboard amp seem to drive them okay at not-insane levels of volume - they sound really sweet paired with the 6.5-inch subwoofer. While I won't change my rating, I do highly recommend getting a sub along with these speakers.
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Reviewed in the United States on April 11, 2025