The #18 awg striped wires are to the SST-2 to an external alarm. The SST-2 uses a summary alarm, which will give an alarm for four different reasons: loss of power, failed temp sensor, ground fault test failure and a ground fault alarm.
A flashing supply light means that the temperature sensor is either missing or bad. Ensure that the sensor is correctly wired to the two blue wires. The system will not function without a sensor. Click here to see more about the Temperature sensor.
When wiring the SST-2 the white and red wires of the controller must be wired together for the unit to have power. This is regardless of the voltage applied to the unit. The white wire powers the controller and the red wire goes to the contact of...
This depends on what you are calling heater cable. Most heat cable has two segments the heat tape and the cold wire. These are usually spliced together in either a high-temperature box or as an in line splice.