Monostable Timer Calculator

Can anyone define pin two in red circle (in, Ov,+vs)?

Pin 2 on a 555 is the trigger input pin, hence the name written in the box /TRG.
TRG = a contraction of TRIGGER, and the / indicates that the signal is active in the low state.

in, 0v, +vs
in = this is the input
0v and +vs, these indicate (badly) that the trigger pulse varies from +vs (the supply voltage) to 0v (zero volts).

JimB

thanks for the kind info JimB, so how can i use this trigger pin in the listed image.
(IC555 Monostable Timer Calculator V1.0)

so how can i use this trigger pin in the listed image.
(IC555 Monostable Timer Calculator V1.0)

Click to expand...

You don't.

All that thing in the link does is calculate the pulse period for given R and C values.

JimB