1 relay S-R flip-flop

    |                                           |
    |                                           |
    |                                           |
    |           RESET                           |
    |----| |----O__O---------------+----( R )---|
    |     R                        |            |
    |           ____               |            |
    |-----------O  O---------------+            |
    |           SET                             |
    |                                           |
    |                                           |
    |                                           |