Communication Services

Normally, an organization that wishes to transmit data uses one of the common carrier services to carry the messages from station to station. Following is a brief description of these services.
Narrow band Service - Usually, this service is used where data volume is relatively low ; the transmission rates usually range from 45 to 300 bits per second. Examples of this are the telephone companies’ typewriters exchange service (TWX) and Telex service.
Voice band Services - Voice band services use ordinary telephone lines to send data messages. Transmission rates vary from 300 to 4,800 bits per second, and higher.
Wide band Services - Wide band services provide data transmission rates from several thousands to several million bits per second. These services are limited to high-volume users. Such services generally use coaxial cable or microwave communication. Space satellites, a more exotic development, have been employed to rapidly transmit data from any part of the world to another part of the world.