I made an RJ11 work with USB on a different detector with these two parts:
Xislet 15" Radar Detector... https://www.amazon.com/dp/B082V1245P?ref=ppx_pop_mob_ap_share
DC 5V to DC 12V USB Voltage Step... https://www.amazon.com/dp/B07J6NYVJV?ref=ppx_pop_mob_ap_share
I have ridgid power tools and purchased these to use my ridgid batteries tobpower the masterbuilt if i needed to. DC 5V to DC 12V USB Voltage Step... https://www.amazon.com/dp/B07J6NYVJV?ref=ppx_pop_mob_ap_share & Ridgid AC86072B 18V USB Portable... https://www.amazon.com/dp/B01K09TFEC?ref=ppx_pop_mob_ap_share
BirdCord seems to get better reviews in general on Elektronauts, works well for me.
I also have (because I was impatient in waiting for the BirdCord): * https://www.amazon.com/gp/product/B08CCX5S96/ * https://www.amazon.com/gp/product/B089SQFCBW/ + https://www.amazon.com/gp/product/B01CJDKPOG/ - Can drive two boxes, including one of the Analogs/OT, but it's heavy + separate power supply * https://www.amazon.com/gp/product/B07J6NYVJV/ (I only tested briefly, I prefer USB-C or the DC output bank above)
DC 5V to DC 12V USB Voltage Step Up Converter Cable - iGreely Power Supply USB Cable with DC Jack 5.5 x 2.5mm or 5.5 x 2.1mm, USB 5V to DC 12V Cable 3ft https://www.amazon.com/dp/B07J6NYVJV/ref=cm_sw_r_cp_tai_bSGuDbJ14KP8J
This with any usb battery pack....
Ripcord seems to have issues for at least some people over on Elektronauts that might be worth reading about.
I have used: * BirdCord * https://www.amazon.com/gp/product/B08CCX5S96/ * https://www.amazon.com/gp/product/B07J6NYVJV/
i got this cheap thing and it works fine https://www.amazon.com/gp/product/B07J6NYVJV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1