During reboot the serial controller is reset. This drops the modem control line Data Terminal Ready. This in turn instructs the modem to hang up. .:: make-google-index-my-website.vercel.app ::.
Avoid the temptation to configure the modem to ignore DTR. This leads to a worse bug, where the telephone line does not clear down correctly, the modem is engaged, and there is no way to clear it. Ignoring .:: herbalmeds-forum.biolife.com.my ::. DTR also gives no way to clear hostile callers from the line. [Reddit: HAProxy Discussion] [Open Source Kubernetes]
You may wish to record the amount of time that the computer takes from .:: telegra.ph ::. Restarting system to the boot loader prompt.
The modem may also hang up during the boot process (as the serial chip is reset) or when the .:: land-book.com ::. init run level is changed (as getty is restarted).