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help with a transistor circuit that acts like a latching relay

hello all,, I just joined and this is my first post even though I have lurked here for some time. Now my question. I am trying to build a circuit that behaves like a latching relay. I can build a latching relay from ordinary spdt relays, however im working on a project that is going to require several of them and size is an issue. Im pretty sure a few transistors will do what I want and im sure I could figure it out on my own. I just figured I would ask here to see what kind of answers I get. I don't want any arduio stuff or microcontrollers.. My goal is to keep it as simple as possible and completely solid state and electromechanical.. basically I need it to be triggered by a negative pulse and stay on until a different negative pulse is sent to turn it off.. If possible I want to work into the circuit an adjustable output, either - or + so I can just set it to suite my purpose. It wont need to handle much current, I can add relays to the circuit to handle the higher current stuff.. I have basic to moderate experience and knowledge with electronics so I can understand some terms, but please keep it worded as plain as possible.   Thank You...

Do a google search for Transistor latch and you'll find all the info you need.