AT&T 75 Wiring Manual page 452

66-TYPE HARDWARE
The yellow field (auxiliary field) connects all 25-pair cables from the auxiliary
cabinet and the AP, when either is used. The yellow field is usually small and is
located at the lower right-hand corner of the purple field.
The white field (station field) connects to the station wiring. The white field
indicates 3-pair station circuits (eight circuits per 25-pair cable) which are routed
through a satellite closet.
The blue field (station field) indicates 3- and/or 4-pair station circuits (eight or six
circuits, respectively, per 25-pair cable). The fourth pair, of the 4-pair station circuit,
is used to supply adjunct power from the cross-connect field on an as-needed basis to
terminals within 250 wire feet length of the cross-connect field.
Figure 4-14 shows a typical cross-connect field installation using 66-type hardware. It is
possible that only a few 66-type connecting blocks will be required in the Trunk/Auxiliary
Field for the green and yellow fields. For this reason, if the 157B connecting blocks are
mounted on a purple 183-type backboard or the 166-type purple backboard equipped with
connecting blocks is used as the Trunk/Auxiliary Field, then some of the extra connecting
blocks in the purple field can be used as the green and yellow fields to save ordering extra
backboards and connecting blocks. When this is done, the green and yellow fields should be
clearly identified to avoid confusion when additional trunks and auxiliary equipment is
added in the future. The white backboards for the connections to the satellite closet must be
ordered from an outside vendor. If blue backboards are used for these connection then the
part of the blue field that is functionally used as the white field, should be clearly identified.
It is also possible that all of the 66-type connecting blocks will be mounted directly onto the
wall without using any colored backboards. If this is the case, all of the cross-connect field
functional colors should be identified on the wall.
4-26