OPERATION:
When de-energized, port ①,③ and ⑤ are connected together, port ② and ④ bleed
through an orifice to port ① . When coil S1 energized, the spool shifts up to block port
⑤ , while allowing flow from ④ to ① and from ③ to ② . When coil S2 energized, the
spool shifts down to block port ⑤ , while allowing flow from ② to ① and from ③ to ④ .