Most likely analogue - a simple DTMF decoder and a couple of walkie-talkes.
Edit: early analogue multichannel R/C used to use resonant reeds that vibrated at different audio frequencies to switch the different functions.
Good info.
Early Westinghouse remote sender/receivers over telephone lines used something similar; the public saw this in action with the "robot" Electro (as well as earlier Westinghouse "robots"). Basically tones sent down the lines to vibrate tuning forks that closed switches. Used for early industrial remote telemetry and control systems - this book is a great history on these machines:
http://www.amazon.com/Robots-Westinghouse-1924-Today-Scott-Schaut/dp/0978584414
A very good addition to one's knowledge bank.