A portion of such a partial multiple A-board is shown in Fig. 379. This view shows slightly more than one section, and the regular answering jacks and lamps may be seen at the bottom of the jack space just above the plugs. Above these are placed the outgoing trunk jacks, those that are in use being indicated with white designation strips. Above the outgoing trunk jacks are placed the multiples of the answering jacks, these not being provided with lamps.

The partial multiple A-section of Fig. 379 is a portion of the switchboard equipment of the same office to which the trunking section shown in Fig. 378 belongs. That this is a large multiple board may be gathered from the number of multiple jacks in the trunking section, 8,400 being installed with room for 10,500. That the board is a portion of an equipment belonging to an exchange of enormous proportions may be gathered from the number of outgoing trunk jacks shown in the A-board, and in the great number of order-wire keys shown between each of the sets of regular cord-circuit keys. The switchboards illustrated in these two figures are those of one of the large offices of the New York Telephone Company on Manhattan Island, and the photographs were taken especially for this work by the Western Electric Company.

Cable Color Code. A great part of the wiring of switchboards requires to be done with insulated wires grouped into cables. In the wiring of manual switchboards as described in the seven preceding chapters, and of automatic and automanual systems and of private branch-exchange and intercommunicating systems described in succeeding chapters, cables formed as follows are widely used:

Tinned soft copper wires, usually of No. 22 or No. 24 B. & S. gauge, are insulated, first with two coverings of silk, then with one covering of cotton. The outer (cotton) insulation of each wire is made of white or of dyed threads. If dyed, the color either is solid red, black, blue, orange, green, brown, or slate, or it is striped, by combining one of those colors with white or a remaining color. The object of coloring the wires is to enable them to be identified by sight instead of by electrical testing.

Wires so insulated are twisted into pairs, choosing the colors of the "line" and "mate" according to a predetermined plan. An assortment of these pairs then is laid up spirally to form the cable core, over which are placed certain wrappings and an outer braid. A widely used form of switchboard cable has paper and lead foil wrappings over the core, and the outer cotton braid finally is treated with a fire-resisting paint.

STANDARD COLOR CODE FOR CABLES

LINE WIRE MATE
White Red Black Red-White Black-White
Blue 1 21 41 61 81
Orange 2 22 42 62 82
Green 3 23 43 63 83
Brown 4 24 44 64 84
Slate 5 25 45 65 85
Blue-White 6 26 46 66 86
Blue-Orange 7 27 47 67 87
Blue-Green 8 28 48 68 88
Blue-Brown 9 29 49 69 89
Blue-Slate 10 30 50 70 90
Orange-White 11 31 51 71 91
Orange-Green 12 32 52 72 92
Orange-Brown 13 33 53 73 93
Orange-Slate 14 34 54 74 94
Green-White 15 35 55 75 95
Green-Brown 16 36 56 76 96
Green-Slate 17 37 57 77 97
Brown-White 18 38 58 78 98
Brown-Slate 19 39 59 79 99
Slate-White 20 40 60 80 100

The numerals represent the pair numbers in the cable.

The wires of spare pairs usually are designated by solid red with white mate for first spare pair, and solid black with white mate for second spare pair. Individual spare wires usually are colored red-white for first individual spare, and black-white for second individual spare.

LINE WIRE MATE
White Red Black Red-White Black-White
Blue 1 21 41 61 81
Orange 2 22 42 62 82
Green 3 23 43 63 83
Brown 4 24 44 64 84
Slate 5 25 45 65 85
Blue-White 6 26 46 66 86
Blue-Orange 7 27 47 67 87
Blue-Green 8 28 48 68 88
Blue-Brown 9 29 49 69 89
Blue-Slate 10 30 50 70 90
Orange-White 11 31 51 71 91
Orange-Green 12 32 52 72 92
Orange-Brown 13 33 53 73 93
Orange-Slate 14 34 54 74 94
Green-White 15 35 55 75 95
Green-Brown 16 36 56 76 96
Green-Slate 17 37 57 77 97
Brown-White 18 38 58 78 98
Brown-Slate 19 39 59 79 99
Slate-White 20 40 60 80 100

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CHAPTER XXVIII
FUNDAMENTAL CONSIDERATIONS OF AUTOMATIC SYSTEMS

Definition. The term automatic, as applied to telephone systems, has come to refer to those systems in which machines at the central office, under the guidance of the subscribers, do the work that is done by operators in manual systems. In all automatic telephone systems, the work of connecting and disconnecting the lines, of ringing the called subscriber, even though he must be selected from among those on a party line, of refusing to connect with a line that is already in use, and informing the calling subscriber that such line is busy, of making connections to trunk lines and through them to lines in other offices and doing the same sort of things there, of counting and recording the successful calls made by a subscriber, rejecting the unsuccessful, and nearly all the thousand and one other acts necessary in telephone service, are performed without the presence of any guiding intelligence at the central office.

The fundamental object of the automatic system is to do away with the central-office operator. In order that each subscriber may control the making of his own connections there is added to his station equipment a call transmitting device by the manipulation of which he causes the central-office mechanisms to establish the connections he desires.

We think that the automatic system is one of the most astonishing developments of human ingenuity. The workers in this development are worthy of particular notice. From occupying a position in popular regard in common with long-haired men and short-haired women they have recently appeared as sane, reasonable men with the courage of their convictions and, better yet, with the ability to make their convictions come true. The scoffers have remained to pray.