Illegal Substitution

[Flags-R-Us]

Where is it stated that a replaced player has 3 seconds to begin leaving the field or be hit with an illegal substitution foul? Is the 3-seconds requirement in the rulebook?   
Thanks

[BIG DON]

3-7-1 page 46 of the 2018 NFHS football rule book.

Between downs any number of eligible substitutes may replace players. Upon meeting the criteria of 2-32-12, replaced players shall begin to leave the field with in 3 seconds.

Now some one can correct me if I am wrong the wording use to say replaced players shall leave the field immediately and we always used the standard of 3 seconds, it was last year or the year before when the Federation finally defined and add the verbiage of 3 seconds   

[ncwingman]

At hand, the oldest rule book I have (2012) has the 3 seconds explicitly stated and it's not denoted as a new addition/rule change. I found a power point of the 2010 rule changes where the substitution rule (and 3 seconds) is mentioned, but it doesn't state exactly what was changed.

[BIG DON]

Thanks for that I can not recall when 3 Second was actually put into the rules but I do remember when I first started 20+ years ago immediately was written in the rules and it was just common practice that we used 3 seconds. When I get home tonight I will check to see if I can find when it was change in the verbiage.   

[GA Umpire]

At hand, the oldest rule book I have (2012) has the 3 seconds explicitly stated and it's not denoted as a new addition/rule change. I found a power point of the 2010 rule changes where the substitution rule (and 3 seconds) is mentioned, but it doesn't state exactly what was changed.

Guys:
2009 was the year of change.  It was shaded in grey in the rules book.

[Flags-R-Us]

Thank you all very kindly.   

[prab]

Guys:
2009 was the year of change.  It was shaded in grey in the rules book.

Wasn't 2009 also the one and only year that the hash marks bisected the yard lines! 

[Ralph Damren]

We swapped 3 seconds for immediately in 2009. Nothing happens immediately when a sub enters the game and we decided to give big ole' Bubba the chance to -one thousand one- shake his head in disbelief - one thousand two - gasp - one thousand three - head to the sidelines thinking the coach must have a brain cramp .