Phone extensions offer extended directory options for situations where using the regular phone system is impractical, such as an office building where potentially hundreds of individual phones are used. Using traditional phone extensions means dialing the building or service's main number and waiting for an operator or automated system to ask for the extension number you are trying to reach. Landlines use only this method, but smartphones have other tricks for expediting calls to extensions.
For iPhones, enter the main number or building number, then press and hold the * key until a comma appears in the number, then enter the extension and send the call as normal.
Android phones can dial extended numbers in two ways: Using the + symbol on the number pad when dialing a number not in your contacts or entering + when adding a new Contact.
To add an extension when dialing, after entering the main number, press and hold the 0 button until a + is added to the number, and then enter the extension number. Use the same steps when entering a number with an extension into a new contact.
Windows phones do not have an option to add an extension when entering a number to dial, but you can add an extension to the number in a contact. First, open your text or email app. Type the main phone number, followed by w, for the extension to instantly dial after the main number, or p, to pause three seconds before the extension number is dialed.
Tap the full number you typed and drag the circles at each end to highlight the entire number, then tap Copy. Load the Start menu and tap People, then swipe over to Contacts and tap New +. Tap the Mobile field and select Paste to add the number. You may need to swipe to the text suggestions menu to get the Paste option. Use the contact card to make the call.