OnSIP can be integrated with the Odoo CRM application by using the following documentation:
In short, add OnSIP as a module and then add your OnSIP username, authorized username and password in the settings.
Once OnSIP is configured, clicking on a number will launch the phone application within Odoo and the call will be placed out the OnSIP service.
Please note, that you must be an OnSIP subscriber with at least a pre-paid PSTN balance in order to make calls via this method.
When placing calls, confirm that the odoo interface is sending a "1" plus area code plus number, e.g. 12125551234.