I am posting this as much for myself as for others, as I usually can't remember how to remedy this situation, it happens to me a lot, the solution is not in the S4 manual, and now I will know where to find the instructions.

When running the S4 in time-of-day program (program #3), I turn the S4 on and the "Clear Ja" option doesn't appear. Aaargh!

Here's how to turn that option on, so that "Clear Ja" is offered when the device is powered up:

1. S4 off
2. Hold "Program + Line Test" toggle UP and turn S4 on.
3. Release "Program + Line Test" toggle.
4. Push "Program + Line Test" toggle UP and release.
5. Display will show "CLr nEIn" if option is disabled or "CLr JA" if enabled.
6. Press yellow button to change setting.
7. Press yellow + red to continue with startup.

Unless you are using the S4 as a standalone device, you should clear its memory regularly. If you do not, eventually the S4's memory will get full, at which point the S4 will stop transmitting RS-232 data to your computer.

It is in the manual page 12