I need a switch that will alternate the flow of electrical current between two diverging wires at a decided rate. Are there switches that function this way? What are they called?
The function you need is a single pole double throw switch. As dave said, that could be a relay, or it could be two MOSFET or transistor switches.
But, you need to provide more info if you want help:
What sorts of loads are you switching (voltage and current).
What sort of control circuit are you using to produce the "decided rate" .
What is the frequency range and duty cycle of the decided rate?
How accurate does the duty cycle need to be?
Does there also need to be an OFF position?
Does there need to be a guaranteed off time when switching (time between loads being powered)?
Can there be overlap when switching load? Or is guaranteed non overlap required?
Does the circuit really need to operate upside down :)
We will probably think of a few more things that need to be decided as we continue.
oscillate every .006 seconds
The load current is 1.25 amps on both sides, the load is purely resistiveThat's too fast for a mechanical relay, so you need to use pass transistors. Can you say more about the application? What is the load current? Are the two load currents equal? What is the nature of the load -- is it inductive?
yes thank youSo you need to use 2 power transistors (probably power Darlingtons based on the current), with the base drive circuits based off of a square wave oscillator at your frequency. You will want to tune the drive circuits to make the current switchover smooth, with little glitching of the total current out of the battery. Are you comfortable taking it from here?