View A of figure 3-2 shows apiece of test equipment that is used to check out electrical or electronic equipment or a system. It also shows the cables that are used to hook the tester to the equipment. The cables have metal or plastic tags at each end showing the cable number and the connector number.

Figure 3-2. - Test equipment cable marking.

View B of figure 3-2 shows the method of connecting the tester to the piece of equipment to be tested. (For a specific tester, the technical manual supplied with the tester shows the method of connection.) The tester shown has four cables. These are numbered W1, W2, W3, and W4. Each cable has two connectors (plugs), one on each end, that are numbered P1 and P2. The cable tag on one end of the cable reads W1-P1, and the other end reads W1 -P2. As shown in the figure, W1-P1 is connected to the receptacle J1 on the tester. W1-P2 is then connected to receptacle J1 on the equipment to be tested. The same procedure is followed for connecting the remaining three cables. The hookup is then complete.

The shipboard and the test equipment cable markings just discussed are only two of many cable-marking systems you may encounter. There are too many systems to attempt to discuss them all. As stated earlier, you should study an equipment or installation technical manual before attempting repairs or connections.

WIRE-MARKING SYSTEMS

Wire-marking systems are used to identify wires in aircraft, shipboard electronic equipment, and power tool and appliance cables.

Aircraft Wire-Marking Systems

All aircraft wiring is identified on wiring diagrams exactly as the wire is marked in the aircraft. Each wire is coded by a combination of letters and numbers (figure 3-3) imprinted on the wire at prescribed intervals along the wire run.

Figure 3-3. - Aircraft wire marking.

Look at figure 3-3. The circuit function letter (P in this example) identifies the basic function of the circuit concerned.

The letter P indicates that the wire is in the dc power distribution system of the aircraft. The wire number, 215, indicates that it is the 215th wire in the dc distribution system. The wire segment letter (A) identifies the position of each wire segment of the circuit. The wire segments are lettered in alphabetical sequence and change each time the wire passes through a terminal or connector. For example, after the wire passes through the first terminal or connector, the segment letter A, as in this instance, would change to B.

The wire size number (4) is the AN wire size. AN wire sizes have more strands for flexibility and are slightly different in circular mil area than AWG (American Wire Gauge) wire sizes. The current-carrying capacity of each is almost the same. The last letter (N) is the ground or phase letter.

The letter N identifies any wire that completes the circuit to the ground network of the aircraft.

In a 3-phase ac power distribution system, a phase letter (A, B, or C) is used as the last letter of the wire marking. If aluminum wire is used as the conductor, ALUMINUM or ALUM will be added as a suffix to the wire identification code.

Q.4 If a wire passes through a connector what portion of the aircraft wire identification number changes?