How to implement a SPDT switch with transistors?

[DS13]

I found plenty of info to do a simple on-off SPST, but wondering if anyone here can share how to implement a SPDT with transistors.

To illustrate in its simplest form, I am looking to have a red LED turn on as a normally closed circuit and when a signal is received by a transistor the red LED would turn off and a green LED turn on.

Ideally, I would like to do this as a momentary switch so that after the signal is raised and subsequently dropped, the original state (Red on / Green off is restored.

Not sure if this is difficult or possible to do without any other components besides trans and resistors.. I spent a couple hours with NPNs and PNPs, frankly by trial and error with some Googling, but could not seem to find a working model.

Any takers?

 

[Stickman393]

I'm hardly an expert here, *but*....

Maybe there's something here that you could achieve by adapting elements from the way Boss pedals handle their bypass switching? IIRC that's a 2 npn 2 n-channel Jfet setup. Not the smallest of parts counts, but I don't see why it couldn't be adapted for your LED setup.

 

[jwin615]

Assuming we're talking a DC signal and low voltage, a mosfet may be the simplest answer