Bell System Practices 50A1 Identification, Installation, Connections, Operation, And Maintenance

BELL SYSTEM PRACTICE
AT& TCo Standard
IDENTIFICATION, INSTALLATION, CONNECTIONS, OPERATION, AND MAINTENANCE
1.

GENERAL

The section contains information on the 50A1
1.01
conference set which permits hands-free
2-way audience participation in a call placed over
the telephone network. This set provides additional
features such as A-lead control, multiple microphone
use, and 2/4 wire operation not provided with the
older 50A (MD) set. The 50A1 is sometimes referred
to as the Portable Conference Telephone.
This section is reissued to include radio
1.02
interference information.
The 50A1 conference set is susceptible to
1.03
radio frequency interference when used near
a high power transmitter. The set can be modified
on a where needed basis at the service center
to suppress this interference. Send the Conference
Telephone to the Indiana Service Center with
instructions to modify per B.S.R.S. 455.217 paragraph
18. "Mod for RFI" will be stamped on the underside
of the base upon completion of modification.
2.

IDENTIFICATION

The 50A1 conference set (Fig. 1) consists
2.01
of a 73B control unit, a modified 220A-58
hand telephone set plus the other accessories listed
in paragraph 2.03 under the Ordering Guide.
A.

Ordering Guide

The 50A1 conference set can be ordered as
2.02
a complete unit as follows.
Set, Conference, 50Al.
•
The following components of the
2.03
conference set are field replaceable and can
be ordered separately:
KS-20653Ll Carrying Case
•
BSP
5l2-630-lll-i0 l_1979.()5-Ql. Jpg
Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Feb 16, 2011 23:00:59
1
SOA CONFERENCE SET
50A1
NOTICE
Not for use or disclosure outside the
Bell ystem except under written agreement
Printed in U.S.A.
Fig. 1-738 Control Unit, Front View
Unit, Control, 73B (includes modified 220A-58
•
hand telephone set)
KS-20660Ll (Green) microphone with 20-foot
•
cord and color-coded plug
KS-20660L2 (Gold) microphone with 20-foot
•
cord and color-coded plug
Set, Hand Telephone, 220A-58 (paragraph
•
5.03)
Lamp, 51A
•
Cord, Handset, H4DB-58
•
KS-20660L3 Lavaliere Assembly (2)
•
KS-20689Ll Power Cord (10-foot length)
•
Cord, Telephone Line, D4BU (25-foot length)
•
Adapter, 225A
•
S
SECTION 12-630-111
Issue 2, May 1979
Page 1