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.
Before connecting the alarm relays leads: An alarm or “power off” condition can be communicated in either of two ways and it is important to make the proper alarm relay connections to achieve the desired result. The middle terminal labeled COM (Common) will always be used. Connect one alarm relay lead to the COM terminal.
NOTE: If the system uses an external alarm light or indicator to come on to communicate an alarm or “power off” condition, connect the other alarm relay lead to the NC or Normally Closed terminal. However, if the system uses an external alarm light or indicator to go off to signal an alarm or “power off” condition, then connect the other alarm relay lead to the NO or Normally Open terminal. Note: if there are no alarm conditions, then when power is supplied to the unit, the Common and Normally Open contacts close to form a complete circuit; otherwise, the Common and Normally Closed contacts will form a circuit.
If using a three-lead wire, it is not necessary to use all three leads when connecting the alarm relay. Use the COM or Common terminal and either of the other two terminals, as desired, based on the information in this paragraph.