I have an ST01 timer that I want to place in a three way circuit that appears to be different than that shown in the directions. My circuit has power (black/white/ground) coming into switch 1 with a three wire setup (red/black/white/ground) going to switch 2 that then goes to the lights (black/white/ground). I would like to replace the second three way switch with the ST01 but I can't figure out how to replace it. All of the combinations I've tried don't make switching happen from both switch positions. Is there a diagram for the way my wiring circuit is set up? Thanks, Steve

One caveat of most In-Wall electronic switches/timers is that the device _must_ be installed at the switch box that has the power, in your case switch #1. In order to install it at switch #2, in your case, you need an extra wire between the switches (to carry the HOT wire), and unfortunately, the bare ground(ing) wire is not permitted to be used to carry current per National Electric Code (NEC).

In your case the wiring for the ST01 is as follows:

Switch box #1: Connect the incoming White wire to the White wire in the 3-wire cable that goes to switch box #2. Connect the incoming (Black) HOT wire to the Black wire on the switch/timer. Connect the Red wire in the 3-wire cable to the Red wire on the switch/timer. Connect the Black wire in the 3-wire cable to the blue wire on the switch/timer. Connect the green wire on the switch/timer to the 2 bare ground(ing) wires. If you have a metal box this connection should also have a pigtail that connects to the box with a green ground screw.

Switch box #2: Remove all of the existing wires from the 3-way switch. The three-way switch will have 2 screws the same color (usually black) and 1 screw (usually brass). For this scenario, one of the black screws will _not_ be used.

Connect the Black wire in the 3-wire cable coming from switch #1, the Black wire going to the lights, and a short Black pigtail together under one wirenut. The pigtail is then connected to the brass screw on the 3-way switch. The Red wire in the 3-wire cable coming from switch #1 is connected to one of the 2 black screws on the 3-way switch (pick one).

In effect you are installing a single switch at switch box #2. In fact, you can use a regular single pole switch if you want too.

To finish, connect the White wire in the 3-wire cable coming from switch #1 to the White wire going to the lights.

Grounding is the same as switch #1 except you'll need a pigtail to connect to the green screw on the 3-way switch.

That's it. You may want to check the battery compartment in the switch/timer, as sometimes they put in a pullout plastic tab to keep it from being energized until needed.

Now, the E1210 is a different animal, and can only be used to replace a single pole switch. You could use it by basically passing the power through to switch box #2 from switch box #1 and then cover switch box #1 with a blank plate. The ST01 could be used that way too, in which case the black on the device connects to the hot, the blue to the lights, and the red on the device is not used, nor will the Red wire in the 3-wire cable between the switch boxes be used.