Activated by the manual button on the CT-A1. Installing CT-6 Probe and Cable. Connected, simply connect a 500 - 1000 ohm resistor between the probe. Only qualifi ed personnel may install or carry out technical service on the product. The customer must only use the product in the manner described in the documentation relating to the product. In addition to observing any further warnings described in this manual, the following warnings must be heeded for all CAREL products.