
das Telefon
telephone
A communication device that allows you to speak with other people over long distances.
Mein altes Telefon mit Wählscheibe funktioniert immer noch.
My old rotary telephone still works.
telephone
Loading your saved state.

telephone
A communication device that allows you to speak with other people over long distances.
Mein altes Telefon mit Wählscheibe funktioniert immer noch.
My old rotary telephone still works.

to answer the phone
To answer an incoming call on a telephone.
Es klingelt schon seit einer Minute, kann nicht mal jemand ans Telefon gehen?
It's been ringing for a minute already; can't someone answer the phone?

to be on the phone
To be having a telephone conversation at the moment; to be talking on the phone.
Der Chef kann Sie gerade nicht sprechen, er ist am Telefon.
The boss can't speak with you right now; he's on the phone.
The word 'Telefon' (telephone) comes from Greek: 'tele' means 'far' and 'phon' means 'voice' or 'sound'. So a telephone is a device for hearing voices over a long distance.
Die Erfindung des Telefons hat die Kommunikation revolutioniert.
The invention of the telephone revolutionized communication.
The preposition 'an' is crucial: 'ans Telefon gehen' (to answer the phone; an das, accusative) describes the action of answering a call. 'Am Telefon sein' (to be on the phone; an dem, dative) describes the state of currently talking on the phone.
Kannst du bitte ans Telefon gehen? Es klingelt.
Can you please answer the phone? It's ringing.
The very common verb 'telefonieren' (to make a phone call/to talk on the phone) is derived from the noun 'das Telefon' (the telephone). It describes the action of having a telephone conversation.
Ich muss später noch mit meiner Mutter telefonieren.
I still have to call my mother later.
mobile phone / cell phone
Handy specifically means a portable telephone for mobile use. Telefon is the more general term and can also refer to a Handy; especially in contrast to Handy, however, it often means a permanently installed telephone.

Zu Hause telefoniere ich mit dem Telefon im Flur.
At home, I make calls on the telephone in the hallway.
Unterwegs telefoniere ich mit dem Handy.
I make calls on my mobile phone when I’m out and about.