# Output gate and activation unit a<t>

In the programming exercise 1, it describe the output gate as follow

• The output gate
1. acts like a βmaskβ that either preserves the values of tanh(πβ¨π‘β©)or
2. keeps those values from being included in the hidden state πβ¨π‘β©

I could get point 1, since the output gate values from 0 to 1. Thus, when output gate is 1, c is preserved.
Yet for point 2, I wonder why it could keep values from πβ¨π‘β©. Should it be πβ¨π‘-1β©?
Since πβ¨π‘β© should be the dependent variable, its means its outcome is determined by the variables , output gate and cell state πβ¨π‘β©. So how come it could βkeepβ its value? Hope mentors or classmates could help. Many thanks.

Hi jackchan.hk,

Point 2. is formulated unfortunately. βThe output gate keeps values from being includedβ is similar in meaning to βThe output gate stops the inclusion of valuesβ. So for clarity, point 2. might read:

β2. stops the inclusion of those values in the hidden state aβ

I hope this clarifies.

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Thanks so much reinoudbosch

This explanation sound and improve much the readibility, love it!!!