OpenIntents

Perform a call to someone specified by the data.

Note: there will be restrictions on which applications can initiate a call; most applications should use the ACTION_DIAL.

Note: this Intent cannot be used to call emergency numbers. Applications can dial emergency numbers using ACTION_DIAL, however.

Calls the entered phone number. Valid telephone numbers as defined in the IETF RFC 3966 are accepted. Valid examples include the following:

• tel:2125551212
• tel: (212) 555 1212

The dialer is good at normalizing some kinds of schemes: for example telephone numbers, so the schema described isn't strictly required in the Uri(URI string) factory. However, if you have not tried a schema or are unsure whether it can be handled, use the Uri.fromParts(scheme, ssp, fragment) factory instead.

Note:   This requires your application to request the following permission in your manifest: <uses-permission id="android.permission.CALL_PHONE" />

See Android documentation, Available intents