The 954 cable is easiest way to connect to your microcontroller/Raspberry Pi/WiFi router serial console port or for programming your VEX Victor BB speed controller.
Inside the big USB plug is a USBSerial conversion chip and at the end of the 36" cable are four wire - red power, black ground, white RX into USB port, and green TX out of the USB port. The power pin provides the 5V @ 500mA direct from the USB port and the RX/TX pins are 3.3V level for interfacing with the most common 3.3V logic level chipsets.
Because of the separated pin plugs, this cable is ideal for powering and connecting up to the debug/login console on the Raspberry Pi or BeagleBone Black. Connect the pins as shown to power the Pi or BBB and establish the RX/TX link.
Also handy for hacking WiFi routers to install alternate OS's, or nearly any other 3.3V logic serial port. This is easier to use than an FTDI cable in many cases because the wires are separated. Note that we call this a "TTL cable" (since that's what they're called) but technically it's CMOS logic.
4 Wire Designation:
Red - 5v
Black - Ground
Green - Rx
White - Tx