1) You posted under ET104C DPST (double pole single throw) 24-hour 4-ON and 4-OFF per-day selectable-voltage timer
DPST means that timer will turn off two wires going to 240Volt Load or two separate 120V Loads
Open following link for example Intermatic ET series wiring diagrams and manual:http://waterheatertimer.org/How-to-wire-Intermatic-ET-series-timer.html
2) Load means whatever electrical device is controlled by timer. ie fan, light, motor, pump, alarm-bell, water-heater, bowling-ball-machine etc.
Line means cable coming from breaker box.
3) If you have a different timer, then add a comment with photo of inside of timer door for possible identification and complete answer.http://www.fixya.com/support/r6568559-post_photograph_fixya_questions_answers
4) Selectable voltage means you have to choose voltage.
Timer come preset for 240Volts.
If you have 120V 208V or 277V, then follow the vague instructions shown on page 2 #2 of manual.
5) Do not apply voltage to this timer before matching selectable voltage setting with circuit breaker voltage.
6) ET104C has 6 terminals and can be wired many different ways depending on Load voltage, etc.
This timer can do a lot of different things.
If you have ET102C with 4 terminals, then add a comment and clearly explain voltage, color of wires, and what breaker you have and what Load you are controlling for best answer.
7) ASSume you have 240Volt cable coming from breaker box, and that you are controlling a single 240Volt Load like a water heater or pool pump.
240Volt cable from breaker will have 2 hot wires called Line 1 and Line 2
Line 1 black wire will attach to both terminal 1 and terminal 3 (use a jumper wire between terminal 1 and 3)
Line 2 red or white wire will attach to both terminal 2 and terminal 5 (use a jumper wire between terminal 2 and 5)
Your 240Volt Load will also have 2 wires.
Load 1 black wire will attach to terminal 4
Load 2 red or white wire will attach to terminal 6
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