you should be able to get a user's manual from the manufacturer website
I had some older ones like the ones in your pictures which worked as an analog telephone(no power required) but also had lots of functions such as saved numbers, speed dial, etc which only worked when the power supply was plugged it. Are you sure you've used the right plug? Some are two lines, some are only one line, with two plugs, for transiting the line through to a fax
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