My last DirecTV receiver, a Hughes-made Sony SAT-A65A, had a very odd bug. If you unplugged or rebooted it, the receiver could not connect with DirecTV billing. There was a test menu screen that could be accessed with a few keypresses that showed, among other things, the number of calls attempted, the number of calls completed, and date/baud rate of the last successful call.
It wasn't unusual, from that menu, to discover that the receiver had made over 300 attempts to dial out, without a single successful connect. The reason for failure was also on that screen, and it was always listed as "No Dial Tone." The phone line was perfectly fine though.
Worse, when it couldn't connect, it would keep trying roughly every hour on the hour...very annoying if you're on the telephone with someone, only to hear the DirecTV box clicking in your ear. It also wasn't unusual for those dialout attempts to disrupt my internet access, back when 56K was still the norm here.
As best as I could determine, it appeared that the modem was trying to dial out without going through the electronic equivalent of removing the phone from the hook first. It couldn't make a connect because it couldn't acquire a dial tone. Through that same
test menu described above, I stumbled across a solution, after much trial/error.
The solution involved entering a modem test screen. From that screen, you could input a phone # for the receiver to use during modem tests (I used to use a local Earthlink #, since I was a subscriber to them for a couple of years), then you had buttons to click for on-hook/off-hook/dial.
All I had to do, to get the receiver to dial out properly, was click the "off-hook" button one time, then instruct the receiver to dial the test #. It dutifully did, and would usually make a connect with the test # at a speed of 2400 baud.
Once that initial forced connect was made, and to this day I still don't understand why, the receiver could then dial out successfully to the DirecTV billing line...until there was a power failure or a receiver freeze-up, which would result in a reboot. Once either would happen, I found it necessary to repeat the above procedure, or the "no dial tone" error would repeatedly begin showing up on the receiver test page again.
I know the above sounds odd, but I can promise you that it happened...over and over and over again.