The Class field contains the speed of the device, if the keyword ACU or Direct is used in the Type field. However, the Class field can contain a letter and a speed, such as C1200 or D1200, to differentiate between classes of dialers, such as Centrex or Dimension PBX.
This differentiation is necessary because many larger offices can have more than one type of telephone network. One network might be dedicated to serving only internal office communications while another network handles the external communications. In such a situation, you must distinguish which line or lines should be used for internal communications and which should be used for external communications.
ACU cua/a - D2400 hayes
Some devices can be used at any speed, so the keyword Any can be used in the Class field. If Any is used, the line matches any speed that is requested in the Speed field of the Systems file. If this field is Any and the Systems file Speed field is Any, the speed defaults to 2400 bps.