In this relay, when a current flows through the coil, it turns it into an electromagnet. The magnet pushes a switch to the left, forcing the spring contacts together, and completing the circuit they're attached to. This is a relay from an electronic, hot-water immersion heater programmer....
Wire the newer phone's board in parallel with the old phone's parts and it ought to work. You may be violating a law or two by connecting an unapproved home-made device to the public telephone system, but if it's electrically the same as the original two phones plugged into a Y-...
This is going to take serious rubbing! Then I used a soft bristle brush & warm soapy water to briskly brush them repeatedly to remove all tarnish and blue goo. I used a little more dish detergent & clean warm water to brush them again and rinsed in warm water. Then I dried them with...