BELL SYSTEM PRACTICES
AT
&
TCo Standard
SECTION 5 1 8-450- 1 00
Issue 3, October 1 976
7 A COMMUNICATION SYSTEM
(COM KEY* 718)
CONTENTS
PAGE
1 . GENERAL
2
2. DESCRIPTION OF APPARATUS
3
570A KSU
3
CONSOLES
1 1
EXTERNALLY MOUNTED APPARATUS
1 1
KEY TELEPHONE UNITS
15
KITS OF PARTS
22
TELEPHONE SETS
25
3. INSTALLATION
3 1
PLANNING
3 1
ORDERING GUIDE
32
INSTALLING
35
A. 570A KSU
35
B. Satellite Wiring Plan
35
C. Telephone Sets
37
4. FEATURES (IDENTIFICATION, OPERATION,
CONNECTIONS, AND TESTING)
38
BASIC FEATURES
38
A. Automatic Button Restoration
38
B. Common Audible
38
CONTENTS
D. Pickup, Hold, and Illumination
E.
Tone and Voice Signaling
F.
2-Path Intercom
OPTIONAL FEATURES
A. CO Ringing
B. External Signaling Circuit
C. Intercom Preset Conference
D. Music-On-Hold
E.
Ring Transfer
F.
Paging and Background Music
G. Power Failure Ringer
H. Power Failure Transfer
I.
Privacy
J.
Privacy Release
K. Recall
L.
Speakerphone
3B Speakerphone
4A Speakerphone
M. Station Busy Consoles
PAGE
4 1
4 1
4 1
43
43
43
44
48
49
5 1
55
55
56
58
59
59
59
59
63
Station Busy Console ( 6A 1) With DSS
C. Multiline Conferencing
*Trademark
40
NOTICE
Not for use or disclosure outside the
Bell System except under written agreement
Printed in U.S.A.
63
Page 1