11 The Relays do the Exchanging
All that's left to do now is add the relays that will connect each source to each destination phone . As I have four lines I will need a set of eight solid state relays arranged so that one of each of the four source lines can be linked to one of the four destinations line via the bridge relay. I've been using the Panasonic AQW210EH throughout with the exception of the ringing relay. As in the bottom left(ish) of the picture, I take four feeds from each of the phone lines and arrange two 18 pin sockets (empty in the picture) to hold the four eight pin relays. At the time the picture was taken I've added copper links to two of the relays so I can dial and link my two phones in either direction, either as source or destination. A more detailed picture shows more copper links added, so we have a relay between each phone and the source and destination lines, each running down a copper strip of the Veroboard, to the right of relays. Each relay will be actuated by a link...