extension number

Translations
внутренний номер
He dialed the extension number to reach the manager.
Он набрал внутренний номер, чтобы связаться с менеджером.
Definitions
An extension number is a short numerical code used within a telephone system to route calls to specific internal lines or devices, allowing users to connect directly to a particular phone or department without going through a central operator.
Words
extension

noun
расширение
number

noun
число