TL-MR6400 v4 - LTE modem for WAN connection

DTR in this context is https://en.wikipedia.org/wiki/Data_Terminal_Ready

And then you might ask what an RS232 terminal signal has to do with a USB connected digital radio... The DTR is mapped to a specific USB control request in the USB Communication class spec. A few years ago Qualcomm started using this request as a suspend/resume signal in their vendor specific QMI/RMNET protocol. So we have to send that request to the modem to wake it. Which is what the DTR patch is about.

(I've been talking about making this behaviour default for all devices for years, but never got around to actually doing that. should probably stop talking about it...)

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Thank you so much for clarifying this. That's very helpful, and finally makes sense to me. Haha, please don't stop talking about it. If something makes things easier for everyone else, then we should certainly be doing it :slightly_smiling_face: