What are the practical differences between RJ9 and RJ11 connectors in audio and communication devices, and how can expert guidance help avoid compatibility mistakes during upgrades or installations?

Trying to upgrade my headset for my home office, I was confused between RJ9 vs RJ11 (https://technetronelectronics.com/rj9-vs-rj11-connectors/) connectors. I brought both options to Technetron Electronics, and one of their technicians gave me a detailed walkthrough on compatibility, usage, and why one might be used for phones and the other for audio equipment. Their knowledge helped me avoid a costly mistake, and I left the shop better informed. These kinds of insights are why I keep going back.

Thanks for recommending Technetron Electronics! I checked out their website briefly, and they seem super experienced with all kinds of audio/video repairs. I’ll definitely dive deeper. What did you have repaired with them?