from top to bottom in the following picture
1. Control Bus Cable with RJ-H connector 4P4C. A 4 wire cable used between boosters and a command station. Maximum length is 300 feet.
2. Cab Bus Cable with RJ12 connector 6P4C. A 4 wire cable used for tethered cabs. Notice the 6 pin connector with only 4 slots being used. This is a regular Cab cable. Can be flat or coiled. Maximum length is 40 feet.
3. Cab Bus Cable with RJ12 connector 6P6C. A flat 6 wire cable can be used for the cab bus and for the Powercab. A six wire cable is required for the Powercab only, and only when the Powercab is being used in the original configuration with the special Powercab panel (PCP). Regular cabs do not need a 6 wire cable but will work with one. This cable carries full track power AND Cab bus when used with the Powercab. Maximum length when used with powercab is 10 feet. For other applications maximum length is 40 feet.