Yes, that's one of the purposes of a transistor... or an analog switch.
It entirely depends on the current and voltage characteristics of what you're doing and how you want to drive it.
Relays provide physical isolation when switched off which a semiconductor doesn't do.
transistors just switch on and off a circuit. I need something that works exactly like a mechanical relay ' when there's a signal it must switch on a circuit and when the signal is gone it must switch on some other circuit'
can u name any solid state relays mr pudding
and ur quote is well mr. beenthere
Look up Solid State Relays or Omron (a leading manufacturer) in a catalog like Mouser
Info that I am guessing at -
You need the relays to switch AC power with a DC control circuit.
You don't need more than standard 120VAC for the output.
The datasheet here includes models that will do that and some variants.
Optocoupling for input output isolation is used in every Solid State Relay I can think of and I may just have a mental habit of thinking of DC output control for Optos and AC outputs controlled with an SSR, when I know that some devices of both names can be set up for either type of output.
I am not sure if you would be making any mistake by calling an OPTO an SSR and an SSR an OPTO.
Sorry I didn't notice earlier that you wanted a Double Throw relay.
I see what you mean about transistors just switching circuits on and off.
But with transistors they made logic chips, computers, and all sorts of other fun stuff.
The SSR or Opto will mostly just take care of switching stuff on and off. It is not that they can't build the logic in and make a DPDT or 18P3T SSR, but it just is not worth it. put your logic or programming together, put an SSR on every output circuit then with the logic and computer to execute have everything plan out all the timing and turn everything on and off as needed.