What is a CODEC?

A coder/decoder IC or circuitry that converts a voice signal into a predetermined digital format for encrypted transmission.

This is the definition.

For more info, please see Wikipedia's article on Codec

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The GSM (Global System for Mobile Communications) uses what type of CODEC for digital mobile radio system communications?

Regular-Pulse Excited (RPE).

This method efficiently codes speech with a minimum amount of errors, when compared with the original voice communication. It allows for minimizing the data use of a communication channel.

For more info, please see Wikipedia's article on Long-term prediction (communications)

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Which of the following codes has gained the widest acceptance for exchange of data from one computer to another?

ASCII.

A code used especially in personal computers.

For more info, please see Wikipedia's article on ASCII

The extended ASCII table is on ASCII Code site, as ASCII Code - The extended ASCII table

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The International Organization for Standardization has developed a seven-level reference model for a packet-radio communications structure.

What level is responsible for the actual transmission of data and handshaking signals?

The physical layer.

• Layer 1:  Physical Hardware - Signaling & Wiring
  
• Layer 2:  Data Link - Frames & Packets
  
• Layer 3:  Network - Datagrams
  
• Layer 4:  Transport - Streams & Segments
  
• Layer 5:  Authentication & Encryption
  
• Layer 6:  Presentation - Encoding
  
• Layer 7:  Application - Message Passing
  

Info above provided by wp2ahg

For comprehensive info on the OSI layers model, please see the Wikipedia's article on the Open Systems Interconnection model (OSI model)

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What CODEC is used in Phase 2 P25 radios?

AMBE

Phase 2 P25 radios were designed to provide land and mobile digital voice/data communications for emergency use such as first responders and for public safety.

They can communicate with legacy analog units. The key is that these radios integrate all users who can share info. In the past, various radio systems did not talk to each other.

For more info, please see Wikipedia's article on Project 25

Also, see P25 Phase 2 site for article on More information about P25 Phase 2

From wp2ahg:

AMBE Advanced Multi-Band Excitation is a proprietary voice CODEC licensed by Digital Voice Systems, Inc. used in Phase 2 P25 radios.

For more info, please see Wikipedia's article on Multi-Band Excitation

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The International Organization for Standardization has developed a seven-level reference model for a packet-radio communications structure.

The _______ level arranges the bits into frames and controls data flow.

Link layer.

• Layer 1:  Physical Hardware - Signaling & Wiring
  
• Layer 2:  Data Link - Frames & Packets
  
• Layer 3:  Network - Datagrams
  
• Layer 4:  Transport - Streams & Segments
  
• Layer 5:  Authentication & Encryption
  
• Layer 6:  Presentation - Encoding
  
• Layer 7:  Application - Message Passing
  

Info above provided by wp2ahg

For comprehensive info on the OSI layers model, please see the Wikipedia's article on the Open Systems Interconnection model (OSI model)

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