State machine implementation

Hi everyone,
I have read the article at: http://www.objectmentor.com/resource...les/umlfsm.pdf
I have managed to compile following code:

Code:

class Turnstile
{
public:
    virtual void Lock();
    virtual void Unlock();
    virtual void Thankyou();
    virtual void Alarm();
};
 
class TurnstileFSM;
class LockedState;
class UnlockedState;
class TurnstileState
{
public:
    virtual void Coin(TurnstileFSM*) = 0;
    virtual void Pass(TurnstileFSM*) = 0;
protected:
    static LockedState lockedState;
    static UnlockedState unlockedState;
};
 
class TurnstileFSM : public Turnstile
{
public:
    void SetState(TurnstileState* s) {itsState = s;}
    void Coin() {itsState->Coin(this);}
    void Pass() {itsState->Pass(this);}
private:
    TurnstileState *itsState;
};
 
class LockedState : public TurnstileState
{
public:
    virtual void Coin(TurnstileFSM* t)
    {
       // t->SetState(&unlockedState);
        t->Unlock();
    }
    virtual void Pass(TurnstileFSM* t)
    {
        t->Alarm();
    }
};
 
class UnlockedState : public TurnstileState
{
public:
    virtual void Coin(TurnstileFSM* t)
    {
        t->Thankyou();
    }
    virtual void Pass(TurnstileFSM* t)
    {
        t->SetState(&lockedState);
        t->Lock();
    }
};
 
LockedState TurnstileState::lockedState;
UnlockedState TurnstileState::unlockedState;

My question is:
1. How do I use this code? Give me an example.
2. Why would I need to 2 global state variables:
LockedState TurnstileState::lockedState;
UnlockedState TurnstileState::unlockedState;

Thanks.