Calling feature for ionic v1 app

ionic-v1
1

im using ionic 1 how can i add app to app calling feature in it.

2

no='1234567890’
window.open(‘tel:’ +no, ‘_system’, ‘location=yes’);

Try this…It is working for me

3

is it possible to make voice call between app to app without tel number ?

4

I Just call from default app.
Contact number comes from ionic app but call will be dial from default app of device

And I think without contact number make voice call between app to app is not possible

5

can we use app to app calling using server ? do we have any third party plugins for accessing the speaker in phone for call in ionic ?