Regarding your remark about telco COs...Not exactly. A telephone company Central Office is a place where (on the Main Frame) all of the local users' telephones "appear." When you pick up your phone, you are now at the Main Frame, and the dial tone tells you that the "Line Equipment" (LE) is now available. If you had no connection to the CO, you would find it impossible to make a phone call. EVERYTHING goes via the CO in your community. And, when you dial (or use the number pad) a number, you go through two selectors and one connector as the call is routed to the correct incoming line (in the same office).