
umschalten
to switch channels
To change the channel on a television or radio.
Schalt bitte um, die Sendung ist langweilig.
Please switch channels; the show is boring.
to switch
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to switch channels
To change the channel on a television or radio.
Schalt bitte um, die Sendung ist langweilig.
Please switch channels; the show is boring.

to switch
To change the mode, setting, or state of a device or system. It can also be used mentally for a change in mindset or concentration.
Nach dem Urlaub fiel es mir schwer, wieder auf Arbeitsmodus umzuschalten.
After the vacation, I found it hard to switch back into work mode.

to transition
In sports, especially soccer, to switch very quickly from defense to offense or vice versa.
Nach dem Ballgewinn schaltete die Mannschaft sofort um und startete einen Konter.
After winning the ball, the team immediately transitioned and started a counterattack.
'Umschalten' (to switch) is a separable verb. The prefix 'um-' comes at the end in a main clause. In subordinate clauses and in the infinitive with 'zu', the verb stays together.
Ich schalte schnell auf ein anderes Programm um.
I'll quickly switch to another program.
When you want to specify what you are switching to, the preposition 'auf' with the accusative is used. This pattern applies to all meanings of the word.
Könntest du bitte auf den Nachrichtenkanal umschalten?
Could you please switch to the news channel?
In addition to the technical meaning, 'umschalten' is often used metaphorically for a mental shift. For example, you can mentally 'switch' from one topic to another or from leisure time to work.
Es fällt mir schwer, nach dem Wochenende mental wieder umzuschalten.
I find it hard to mentally switch back after the weekend.
This meaning is typical of technical language in sports, especially soccer. It describes the quick transition between attacking and defensive play.
Die Mannschaft ist bekannt dafür, nach einem Ballverlust langsam umzuschalten.
The team is known for transitioning slowly after losing the ball.
to change / switch
Both words can express changing channels while watching television. Wechseln describes changing the channel in general, while umschalten emphasizes deliberately changing it using the remote control or a selection. For the specific action of operating the controls, umschalten is more suitable; in a neutral statement about the new channel, wechseln is enough.

In der Werbepause schaltete ich mit der Fernbedienung auf den anderen Sender um.
I switched to the other channel with the remote during the commercial break.
In der Werbepause wechselte ich den Sender.
I changed the channel during the commercial break.