1. Education verification: Returnees will verify the authenticity of the education and certificates provided by employees, including education, school, major and other information.

2. Work experience survey: the transferred personnel will contact the employee's former employer to verify the employee's work experience, position, job responsibilities and performance during the on-the-job period.

3. Personal credit investigation: Returnees may conduct personal credit investigation, including employees' credit records and debts, to ensure that employees have no bad credit records or debt problems.

4. Internal background investigation of the company: Callback personnel will contact relevant departments or personnel within the company to find out the qualifications, performance, reward and punishment records of employees.

5. Criminal record investigation: Returning personnel usually check employees' criminal records to ensure that employees have no major criminal records or illegal acts.

It should be noted that the specific content and depth of ringback tone may vary from company to company and position. At the same time, before any callback, the employee's consent must be obtained in advance, and relevant laws and regulations must be observed to ensure that the employee's privacy is protected.