with the rear grommet is recommended. These extra means  have inherent penalties and should be considered only where  other means cannot be used. Unwired spare contacts should  have a correctly sized plastic plug installed. Connectors must be installed in a manner that ensures  moisture and fluids drain out of and not into the connector  when unmated. Wiring must be routed so that moisture  accumulated on the bundle drains away from connectors.  When connectors must be mounted in a vertical position,  as through a shelf or floor, the connectors must be potted or  environmentally sealed. In this situation, it is better to have  the receptacle faced downward so that it is less susceptible  to collecting moisture when unmated. A rear accessory back shell must be used on connectors that  are not enclosed. Connectors with very small size wiring, or  subject to frequent maintenance activity, or located in high- vibration areas must be provided with a strain-relief-type back  shell. The wire bundle should be protected from mechanical  damage with suitable cushion material where it is secured  by the clamp. Connectors that are potted or have molded  rear adapters do not normally use a separate strain relief  accessory. Strain relief clamps should not impart tension on  wires between the clamp and contact.  [Figure 9-162] Sufficient wire length must be provided at connectors to  ensure a proper drip loop and that there is no strain on  termination after a complete replacement of the connector  and its contacts. All wiring needs to be protected from damage. However,  coaxial and triaxial cables are particularly vulnerable to  certain types of damage. Personnel should exercise care while  handling or working around coaxial.  [Figure 9-163]  Coaxial  damage can occur when clamped too tightly, or when they are  bent sharply (normally at or near connectors). Damage can  also be incurred during unrelated maintenance actions around  the coaxial cable. Coaxial cable can be severely damaged on  the inside without any evidence of damage on the outside.  Coaxial cables with solid center conductors should not be  used. Stranded center coaxial cables can be used as a direct  replacement for solid center coaxial.  [Figure 9-164]  Coaxial  cable precautions include: Figure 9-163.  Coaxial cables.  •  Never kink coaxial cable. •  Never drop anything on coaxial cable. •  Never step on coaxial cable. •  Never bend coaxial cable sharply. •  Never loop coaxial cable tighter than the allowable  bend radius. •  Never pull on coaxial cable except in a straight line. •  Never use coaxial cable for a handle, lean on it, or  hang things on it (or any other wire). Wire Inspection Coaxial Cable Wire Support  Drainage Aircraft service imposes severe environmental condition on  electrical wire. To ensure satisfactory service, inspect wire  annually for abrasions, defective insulation, condition of  terminations, and potential corrosion. Grounding connections  for power, distribution equipment, and electromagnetic  shielding must be given particular attention to ensure that  electrical bonding resistance has not been significantly  increased by the loosening of connections or corrosion. Switches are devices that open and close circuits. They  consist of one or more pair of contacts. The current in the  circuit flows when the contacts are closed. Switches with  Electrical System Components Switches Figure 9-162.  Backshells with strain relief. 9-96