ISDN, Integrated Services Digital Network, was the digital upgrade to analog phone lines. It carried multiple voice or data channels over a single connection and was a common business phone line before VoIP.
Carriers are decommissioning ISDN worldwide. Businesses are moving to SIP trunking and VoIP, which deliver more channels at lower cost over the internet.
Frontdesk gives you a business number answered by an AI receptionist that picks up every call, qualifies the caller, books the appointment, and logs the whole conversation to your CRM.