One of my clients has a landline phone which has problems occasionally. Sometimes it won’t receive calls and sometimes it won’t place calls. This phone setup isn’t a conventional one – it requires a cellular receiver from ATT. An ordinary telephone plugs into it’s RJ-45 connector. Then the telephone line to the building wiring is connected to another RJ-45 jack. When it has problems, I used to try reprogramming it with the manual which didn’t work usually. Now, I turn off the power, disconnect the electrical power cord and remove the battery for a minute or two. This action clears any weird electrical state it’s in and always works.