I have two corded phone lines that I want to connect both of them to one telephone device. The phone must be connected to line 1 by default, and it switches to line 2 when it rings. I made a simple circuit to detect line 2 ring signal that turns on a 2-contact relay to switch lines. It works well when the relay powered from an external supply, But I want it to be a small box beside the telephone device and I don't want to uses an external power supply. The problem is that powering the relay from the phone line draws about 35mA that causes the phone to be answered immediately as it rings. Is there any idea to solve this problem? Like electronic switch replacement for the relay. Note that I don't want to get power from line 1.
(I will add a timer and end-of-call detection circuit to this circuit to avoid switching back to line 1 while using line 2 later.)