philco: World's Fair; 39-116RX (39-116): Remote Operation
(This was posted here several months ago but it seems to have vanished, so this is a repost - too bad too, because I had pictures and everything).
Here is my definitive version of how the remote receiver works:
1. In the beginning, the station selecting switch (SSS) can be in any one of 8 different positions corresponding to the last station tuned - it doesn't matter which one.
2. Receiving the first pulse from the Mystery Control (MC) causes the holding relay to engage (and it must remain engaged during steps 3-5 below). The first pulse also causes the stepping relay to advance its ratchet one position. However at this point it does not yet cause the SSS to move. (You are still tuned to the last station you were listening to).
3. Pulses no. 2 and 3: these are for volume control. They also do not move the SSS.
If pulse 2 is extended (by way of pressing down on the fingerstop on the MC), then the volume control motor is activated in the "down" direction for as long as the fingerstop is depressed. If there are three pulses and the third is extended, then the volume is raised. If there are two or three pulses but they are not extended, then nothing happens.
4. When the fourth pulse (if any) is received, the pawl on the SSS (secondary) ratchet is released, causing the spring on the secondary ratchet to quickly rotate the SSS back to station 1. This happens very fast - it literally snaps back, in less time than the inter-pulse gap. (In my radio, I had to clean and lube the SSS and exercise it a few times before this would happen. The spring is strong enough, but not that strong).
5. If any further pulses are received, each one will cause the SSS to advance one more position. The SSS has already been pulled back to station one in step 4 above. If no further pulses are received, it means you intended to tune station 1 and we go right to step 6. Otherwise, the 5th pulse causes it to advance one position and selects station 2, the 6th pulse selects station 3, etc. up to the 11th pulse which selects station 8.
6. When no more pulses are received, the holding relay drops out and the SSS stays where ever it was when it got the last pulse. The cycle is complete.
7. The next time you twist the dial on the Mystery Control, the entire process starts over again with step 1.