D2
+------------------->|--------------------+
| a |
| Ry1-1 D3 |
+-----+----+---o o------o--->|---+-----+----+
| | | | | | a | | |
| | | | | | | | |
+| [D1] [Ry1] |> |<-' | <| Ry2-1 | [Ry2] [D4]
----- |a | | | | | |a
|Power| +----+ o o------+ | +----+
|Supp.| | | | +| | |
|12 V | | | [NiMh] ---- / ---
----- | [LOAD] | |Smrt| \<--[1K]--/ \TL431
-| | | v--o |Chgr| / ---
| | | ---o ---- \ 50K |
| | | Ry2-2| -| | |
| | | | | | |
+-----+-----------+------+------+----+----------+