Simulate a key press

Hi i have some kind of powerplug schedullers that have a button that you can press for the on/off this button allow you to put the plug in on/off or auto... I want to simulate that button pressed from arduino the board with buttons is this one...

how can i make arduino make what the button does(my guess) make a short between the 1.2v and ground.... ?

Just curiosity:

this board also makes a newbie in electronics like me some questions they use a 48vdc relay for the on/off but they only have a small batt 1.3v 40mah and the 230v ac power .. i can't see any power controller chip.. how the hell they make the 230v ac in the 48vdc ?

Thanks for the warnings i'm taking very attention to the 220v.. I measure the 1.3v disconnected from the grid... Part of the circuit is for sure on 220v but other part can't be... that little battery 1.2v will blow for sure if 220v where there.. i really don't want to mess around with the circuit i just want to simulate that key press. this timers cost-me 4? if i go to buy all the things to build one with arduino wil cost me the double and housing will not be so fancy..

i will have look at that "optically-isolated coupler "... But if i can have my arduino controlling this would be perfect..

Some more pics

From the "main board" to the "logic" board where buttons and lcd are you have only 3 small wires... I measured With no power... and i see 1.3v (the batt) groud, and other that must be who sends the order to the relay on/off

In that case I would use a small reed relay since it doesn't care what the voltage is across the contacts.

how do i connect this to arduino and to the board =?

Thanks

Look at this document:-

Don’t forget the reverse polarity diode if you do connect this directly to the arduino.

Hi I have this one over here on local shop http://pt.mouser.com/ProductDetail/Magnecraft/W107DIP-5/?qs=sGAEpiMZZMv4tz1TW%2fArE91JV6zZx01CphrYo8CcT0Y%3d Will it work ?

i'm bit lost what to connect to what , this is this chip diag

2 pins should be the ones from the board (i will try to solder 2 cables to the board).. the other shoud be +5v & ground from arduino and a digital pin from arduino to do the on off, right ?

but where to i connect them to this chip ?

thanks