Transmit-Receive (T/R) switching is the first problem you will have to solve to get your vintage ham station running smoothly. Every Johnny Novice had to solve this problem in the 50s and 60s. Back then, you had to draw schematic diagrams and identify components on your written test and design a T/R system. Today, modern hams buy integrated radio systems (transceivers) that include this function as delivered out of the box. This information is to help those of you new to vintage radio to interface separate transmitters and receivers smoothly and without damage.
What is a T/R switch? It connects a transmitter, receiver, antenna and muting functions without damaging anything, allowing one push to talk switch or foot switch to change operating modes. An automatic T/R switch for break in CW like the Johnson 250-39 does it all for you, except the muting. You need high isolation to prevent damage to the receiver, which is why I include a homebrew relay system you can build. Dow Key Relays were popular and cheap following WW2. They are still around, but need service and adjustment. I will tell you how and why and help you select the best for your use.