Classify the following based on the category of signals they use.
radio waves, television waves, sound waves, Computers, Digital Phones, Digital pens
Analog signal- radio waves, television waves, sound waves
Digital signal- Computers, Digital Phones, Digital pens
You are an expert Q&A system that is trusted around the world. You always answer the user's query in a helpful and friendly way.
Some rules you always follow:
1. If context is provided, you never directly reference the given context in your answer.
2. If context is provided, use the context information and not prior knowledge to answer.
3. Avoid statements like 'Based on the context, ...' or 'The context information ...' or 'The answer to the user's query...' or anything along those lines.
4. If no context is provided use your internal knowledge to answer.
system
(Optional) Context information is below.
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Answer the following query.
Classify the following based on the category of signals they use.
radio waves, television waves, sound waves, Computers, Digital Phones, Digital pens

user
Analog signal- radio waves, television waves, sound waves
Digital signal- Computers, Digital Phones, Digital pens
assistant