Selecting a CRM is optional and is not required for dialer functionality.
If you have a business CRM, then you can integrate with Auto dialer which helps you to search contacts within the CRM to find the contact information matching the incoming or outgoing number during call or SMS. So this will make you aware about who’s calling or being called and you can see their profile page in CRM during incoming calls. Auto dialer supports several leading CRMs such as Salesforce, ZOHO, Hubspot, Followupboss etc.
On choosing any one of the supporting CRMs, Numbers shown in any pages of the CRM will be highlighted with blue color which is used to make click to Call, SMS and ask user option to choose call or SMS functionality.