Open.

The first price the security traded at during the current interval.

Syntax: Open(Interval, [Ref], [Symbol])

Interval = Required. 

[Ref] = Optional.

[Symbol] = Optional.

Examples:

Open(15,,YHOO)

The first price YHOO traded at during the current 15 minute interval.

Open(60,,)
The first price the security on the current line traded at during the current 60 minute interval.