How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want a complete, ready-to-wear corded headset for your Cisco desk phone, choose MKJ RJ9; if you need a Y-splitter so a trainer and a trainee can share one live call on two Plantronics-style QD headsets, choose Xintronics Training Headphones Adapter.
These two products get compared a lot because both show up in "call center headset" searches, but they solve completely different problems. One is a headset. The other is a cable that lets two headsets share a phone. I'll break down the design, the specs and the real-world fit so you can pick the right one on the first try.
• MKJ RJ9 — biggest strength: a full binaural headset built for Cisco IP phones, with a noise-canceling mic, wideband audio, a 330° rotatable mic boom and a 180° rotatable headband.
• MKJ RJ9 — biggest trade-off: it's locked to the RJ9 headset port on Cisco desk phones. No computer, laptop, mobile phone or PC use at all.
• Xintronics Training Headphones Adapter — biggest strength: a QD Y-splitter that lets two Plantronics-style quick-disconnect headsets share one laptop or landline call, with a 4.2-foot cable and a 12-month warranty.
• Xintronics Training Headphones Adapter — biggest trade-off: it is not a headset and it is not a standalone device. You still need two QD headsets and a connecting cord to make it work.
• Choose MKJ RJ9 if you're the person actually taking the calls and you want one headset you plug straight into your Cisco phone.
• Choose Xintronics Training Headphones Adapter if you're the supervisor or trainer who already owns Plantronics QD headsets and wants to listen in on a live call.
The MKJ RJ9 is a corded, dual-ear (on-ear) headset with a noise-canceling microphone, and it's aimed squarely at people who live on a Cisco desk phone all day. The spec sheet lists it as compatible with a long run of Cisco IP phones — the 6900, 7800, 7900, 8900 and 9900 series, including specific models like the 7821, 7841, 7941G, 7942G, 7945G, 7960G, 7975G, 8841, 8865 and 9975. That's the headline: it's not a universal headset, it's a Cisco RJ9 headset, and that's the whole point.
What it does best is handle long shifts. The design details tell the story: a 330° rotatable microphone arm so you can position the mic on whichever side you prefer, a 180° rotatable headband to fit different head sizes, and on-ear cushions listed for all-day wear. There's a quick disconnect feature too, which matters more than people expect — you can stand up and walk away from your desk without pulling the headset off, and if you later want to use the headset on a different device, you keep the headset top and just swap the cable. The headband is stainless steel, the cord is Kevlar-reinforced, and the ear cushions and body use PU and plastic — all details that speak to surviving chair wheels and daily abuse rather than sitting pretty on a shelf.
Audio-wise, the sheet lists wideband audio technology for clearer, less fatiguing listening, a noise-canceling mic to filter background noise, a dynamic driver, a 20 Hz–20,000 Hz frequency range and 2200 ohm impedance. There's also a built-in acoustic circuit designed to protect against sudden loud bursts — a real consideration if you take a high volume of calls. The mic uses push-button control and sound isolation for noise control.
Who should buy it: call center agents, customer service reps, home-based phone workers and anyone whose daily tool is a Cisco IP phone with an RJ9 headset jack. Who should skip it: anyone who wants to use a headset with a computer, laptop or mobile phone. The sheet is blunt about this — it does not work with those. It's also not for Cisco SPA phones, and it won't help you if your phone lacks an RJ9 headset port. If price matters to you, check the current price on Amazon.
The Xintronics Training Headphones Adapter is a different animal entirely. It's a QD Y-splitter cable — model XVTQD — that lets two Plantronics-style quick-disconnect headsets connect to the same laptop or landline phone so a trainer and a trainee can both hear the same live call. If you've ever run a call center coaching session by holding a handset to someone's ear, this cable is the fix.
The compatibility list is specific, and that specificity is the most important thing to understand. It works with Plantronics QD headsets — H251, H251N, H261, H261N, HW291N, HW301N, HW710, HW720, and all H-series and HW-series headsets — plus same-style QD headsets from TruVoice, VoiceJoy, Wantek and Daily. It does not work with Jabra GN, Yealink, MAIRDI or Sennheiser EPOS headsets. That's not a knock on the product; it's just the reality of quick-disconnect standards. Check your headset's connector before you buy.
What it does best is plug-and-play simplicity. Connect two QD headsets to a computer through a USB QD adapter, or to a landline phone with an RJ9-to-QD adapter cable. The 4.2-foot cable gives you enough reach for two people to sit side by side during a session. The build is PU material over high-purity copper conductors, which the sheet describes as providing secure insulation and toughness for long-term use. It's lightweight, male-to-male, and rated for business calls and call center training, indoor use. It also carries a 30-day replacement and 12-month warranty.
Who should buy it: call center supervisors, team leads, QA monitors and trainers who already own Plantronics QD headsets and need two people on one call. Who should skip it: anyone who needs an actual headset, anyone whose headsets aren't Plantronics-style QD, and anyone who doesn't want to buy the extra connecting cord — the sheet notes you need two QD headsets and one telephone connecting cord to set it up.
• Best for taking calls yourself → MKJ RJ9. It's a complete headset, not a cable.
• Best for training or monitoring a live call → Xintronics Training Headphones Adapter. Two headsets, one phone.
• Best for Cisco IP phone users → MKJ RJ9. The compatibility list is long and Cisco-specific.
• Best for Plantronics QD headset owners → Xintronics Training Headphones Adapter. It's built around that connector standard.
• Best for all-day comfort on long shifts → MKJ RJ9. Rotatable headband, rotatable mic boom, on-ear cushions and hearing protection built in.
• Best for laptop or landline flexibility → Xintronics Training Headphones Adapter. It works with either, provided you have the right adapter.
• Best for durability under daily office abuse → MKJ RJ9. Kevlar-reinforced cord and a stainless steel headband.
• Best for warranty coverage → Xintronics Training Headphones Adapter. The sheet lists a 30-day replacement and 12-month warranty.
My Verdict
No. The data sheet states plainly that this RJ9 headset does not work with a computer, laptop, mobile phone or PC. It's designed for Cisco phones that have an RJ9 headset port.
No. The sheet lists it as compatible with Plantronics QD headsets and same-style QD headsets from TruVoice, VoiceJoy, Wantek and Daily — but explicitly not Jabra GN, Yealink, MAIRDI or Sennheiser EPOS.
Yes. It's a splitter, not a headset. The sheet notes you'll need two Plantronics QD headsets and one telephone connecting cord to complete the setup.
It depends on the job, not the price. If you need a headset, only the MKJ RJ9 solves that problem. If you need to share a call between two headsets, only the Xintronics adapter does that. Check the current price on Amazon for either before deciding.
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