AT&T System 75, Wiring Diagram

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CHAPTER 4. STATION WIRING
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4.
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11.
Mount base of 551A key to 77A bracket using screws provided with
bracket.
Remove housing from 500- or 2500-type telephone.
Connect wire from red lead (R) on telephone through 551A key to
yellow and/or black lead on telephone.
Replace cover on 551A key.
Place groove in bracket over lip of telephone base (Figure 4-38).
Replace telephone housing.
Repeat Steps 2 through 8, as required.
Connect telephones to the information outlets.
Install patch cords/jumper wires between the switch side and the
terminal side of the station distribution field.
Figure 4-38. Ground Start Key Installation
4-66