Good evening to everyone. I have a cordless phone brand PANASONIC MODEL KX-TGA355LA, Well what it has is the following, It turns out that he works with a voltage of 3.5, but does not turn on is as if he had no voltage. Well, what is strange to me is that if I put a voltage of 9 volts, it works well. What could I have to not do it with its voltage of 3.5 volts, could you help me in this fault much to thank. Thank you.

the 9V where you connected them