Originally developed for billing purposes in the telephone network, ANI is also crucial in emergency services and various business applications. 

• Caller Identification: ANI provides the recipient of a phone call with the caller's telephone number, regardless of whether the caller's number is unlisted or caller ID blocking is activated.

• Use in Emergency Services: In emergency services, particularly 911 calls in North America, ANI is used to help identify the location of the caller quickly. This is crucial for dispatching emergency services accurately and promptly.

• Billing and Routing: Originally, ANI was used by telephone companies for billing and routing purposes. It helped in identifying the calling party and ensuring that the call charges were correctly allocated.

• Difference from Caller ID: While similar to caller ID, ANI is distinct in that it cannot be blocked by the caller. ANI is also more reliable for identifying the origin of a call, which is vital for services like toll-free numbers (e.g., 800 numbers in the United States).

• Business Applications: In business settings, ANI is used for customer identification, call routing to appropriate departments, and security verification processes. It enables businesses to tailor their customer service based on the incoming call information.

ANI is a fundamental technology in telecommunication that enhances both service delivery in emergency situations and operational efficiency in business environments.