RCA 76-B2 User manual

RCA Consolette
Type 76-B2
(MI -11613-B)
Type 76-B4
(MI -11613-C)
Power Supply
(MI -11301-B)
RADIO CORPORATIOn OF AIflERICA
RCA VICTOR Division CAMDErl, fl. J.
1B-24454

BROADCAST EQUIPMENT
INSTRUCTIONS
RCA Consolette
Type 76-B2
(MI -11613-B)
Type 76-B4
(MI -11613-C)
Power Supply
(MI -11301-B)
RADIO CORPOR ATIOrl OF A MERICF1
RCA VICTOR Division CAMDE11, 11. J.
PRINTF'D IN U. S. A.
4136

Table of Contents
Page Page
Part I Installation Override Switch 16
Emergency Program Channel 16
Technical Data iii Emergency "B" Supply 17
Description 1Relay Operation 17
Speaker Relay Interlock 17
Associated Equipment 2Light Relay Interlock 17
Microphones 2Speaker Relay Interlock (Two or Three Studio
Microphone Stands 2Operation) 19
Transcription Turntables 2Light Relay Interlock (Two or Three Studio
Recorders 2Operation) 19
Recording Amplifiers 2Speaker Relay Interlock (Single Studio Operation) 20
Loudspeakers 2Light Relay Interlock (Single Studio Operation). 20
Signal Lights and Relays 4Suggested Operating Procedure 20
Power Supply 4To Place a Program on the Air 20
Conduit Terminating Box 4To Audition Studio B while Studio A is on the Air.. 21
6 db Pad for Telephone Lines 4To Cue Studio B from Studio A and then place
BR -84 Rack or MI -11500 Wall Box 4Studio B on the Air 21
Radiotrons 4To Cue Studio B from a Cue Line and then place
Wall and Floor Outlets 4Studio B on the Air 21
Locating and Connecting Equipment 7To Talk Back to Studio A or Studio B 21
Connections to 76-B2 and 76-B4 Consolettes 7Announcing 21
Audio Input Connections 8Emergency Use of Monitor Amplifier 21
Audio Output Connections 8Network Monitoring 21
Connecting Associated Equipment 9
Addition of Signal Lights 9Part III-MI-11301-B Power Supply
Studio "On Air" and "On Audition" Signal Lights 9
Control Room On Air Relay 10 Technical Data 25
Announce Booth Speaker and Signal Light Relays 10
Console Signal Lights 10 Description 25
Instantaneous Recorder 10 Installation 26
Mounting 26
Conduit List for Types 76-B2 and 76-B4 Connections 26
Consolettes 11 Loudspeaker Field Supply 26
Emergency Switch 26
Part II-Operation Hum Adjustment 27
General 15
Program Channel 15 Part IV Maintenance
Audition Channel 16
a. Monitoring 16 Inspection and Checking 31
b. Auditioning 16 Care of Pushbutton Switches 32
c. Cueing 16 Care of Key Switches 32
d. Talk -Back 16 Voltage Measurements 32
Remote Line Cue and Phone 16 Replacement Parts 33
a. Cue 16
b. Phone 16 List of Parts 33

ii
List of Illustrations
Page
Figure 1-Type 76-62 Consolette with Door Open 1
Figure 2-Type 76-62 Consolette with Chassis Raised 3
Figure 3-6 db Pad for Telephone Lines 4
Figure 4-Suggested Recording Setups 5
Figure 5-Front Panel Layout .5
Figure 6-Relay Mounting Cabinet 6
Figure 7-Installation Diagram 6
Figure 8-Mounting Dimensions 7
Figure 9-Schematic of VU Meter and Pad 8
Figure 10-Loudspeaker Connections 9
Figure 11-Typical Conduit Layout 13
Figure 12-Simplified Block Diagram of Types 76-62 and 76-64 Consolettes 14
Figure 13-Announce Booth Relay Connections 17
Figure 14-Simplified Schematic of Control Circuits 18
Figure 15-Simplified Block Diagram of Types 76-62 and 76-64 Consolettes 22
Figure 16-Schematic Diagram (W-131973) 23
Figure 17-MI-11301-B Power Supply 25
Figure 18-Mounting Dimensions (MI -11301-B Power Supply) 26
Figure 19-Interior View of Power Supply 27
Figure 20- Wiring Diagram (MI-1 1301-BPower Supply) 28
Figure 21-Schematic Diagram (MI-1 1301-BPower Supply) 29
Figure 22-Rear View of Power Supply Chassis 30
Figure 23-Relay Mounting Plate Wiring 33
Figure 24-Line Transformer Wiring 34
Figure 25-Preamplifier Mounting Plate Wiring 35
Figure 26-Program Amplifier Mounting Plate Wiring 36
Figure 27-Monitor Amplifier Mounting Plate Wiring 37
Figure 28-Front Panel Wiring (W-131969) 39
Figure 29-Overall Wiring Diagram (W-131681) 41

iii
TECHNICAL DATA
Power Required
One MI -11301-B Power Supply or a -c, d -c supply
as follows:
a. D -C Plate Supply
Term. Volts Milliamperes
Radiotrons*
11 RCA -1620 or 11 RCA-6J7t
2 RCA -1621 or 2 RCA-6F6t
2 RCA -1622 or 2 RCA-6L6t
tMay be used when maximum uniformity of
characteristics, and minimum of microphonics,
116 375 62.0 hum, and distortion are not required.
115114 210278 1.25.1 Inputs
104 285 42.0 a. Six 30- or 250 -ohm microphone inputs
105 220 4.6 (balanced )
Reg. 245 16.0 b. Six line inputs, 150, 300, and 600 ohms
106 (balanced)
Emerg. 200 13.0 c. Two 250 -ohm transcription inputs (unbalanced )
b. A -C Filament Supply
Term. Volts Milliamperes
d. One 250 -ohm talk -back microphone input
(balanced )
112 and 113 6.2 2.7 e. Five 20,000 -ohm monitor cue lines (balanced )
109 and 110 6.2 1.6 Outputs
107 and 108 6.2 0.3 a. One 500- to 600 -ohm line
101 and 102
c. D -C Relay Supply
6.2 2.4 b. Three 15 -ohm monitor lines
c. One high -impedance headphone output (2,000
Term. Volts Milliamperes to 5,000 ohms)
117 and 118 60 100 Line Output Noise Level
Gaina. Microphone Input to Line Output: 112+2 db
b. Transcription Input to Line Output: 81 +1 1/2 db
c. Line Input to Line Output: 54+1 1/2 db
d. Microphone Input to Monitor Output:
110+2 db
e. Line Input to Monitor Output: 54+2 db
f. Transcription Input to Monitor Output:
80+2 db
g. Cue Input to Monitor Output: 34+2 db
h. Talk -back Input to Monitor Output: 95 +2 db
i. Line Output to Monitor Output: 33 ±2 db
j. Microphone Input to Emergency Line Output:
91+2 db
k. Remote Line through Override: 27 +21/2 db
1. External Record: 90+2 db
m. Remote Talk -back: 77+2 db
Line Output Level
Normal: +18 dbm** with 0.5% rms harmonic
distortion from 50 to 7,500 cycles
Maximum: +26 dbm** with 1% rms harmonic
distortion from 50 to 7,500 cycles
Microphone Input at -50 dbm, to Line Output
at 18 dbm** output (68 db system gain): -68 db
Microphone Input to Monitor Output at 4 watts
(+36 dbm**) output (86 db system gain ): -68 db
Distortion
a. Microphone Input to Line Output: 0.5% rms
harmonic distortion from 50 to 7,500 cycles,
with normal output of +18 dbm**
b. Microphone Input to Monitor Output: 11/2%
rms harmonic distortion from 50 to 7,500
cycles at 4 watts output
Frequency Response
a. Microphone Input to Line Output: +2.0 db
from 30 to 15,000 cycles
b. Microphone Input to Monitor Output: +2 db
from 30 to 15,000 cycles (audition channel)
Monitor Power Output
a. 4.0 watts ( +36 dbm**) with 11/2% rms
harmonic distortion from 50 to 7,500 cycles
b. 8.0 watts ( +39 dbm**) with 3% rms harmonic
distortion from 50 to 7,500 cycles
Physical Specifications
Width 39 inches
*TRADEMARK RADIOTRON- REG. U. 5. PAT. OFF. BY RADIO CORPORATION OF AMERICA
**dbm = decibel level referred to one milliwatt sine wave power.
Depth
Height
Weight
17 inches
10 1/2 inches
135 pounds

1
TYPES 76-B2 AND 76-B4 RCA CONSOLETTES
PART I
Installation
DESCRIPTION
The Type 76-B2 (MI -11613-B ) and Type 76-B4
(MI -11613-C) Consolettes have been designed for
use in Broadcast Audio installations to provide a
complete and flexible control system in one con-
veniently arranged unit. All the controls necessary
for switching and mixing the audio outputs of
microphones, transcription turntables and remote
lines, as well as for auditioning and monitoring,
are contained in a single cabinet. The Consolette
may be used as a complete control system for a
small station, or to control a single studio in larger
installations.
The Consolette consists of a metal cabinet con-
taining four pre -amplifiers, a program amplifier, an
eight -watt monitoring amplifier, two line trans-
formers and three loudspeaker relays. A VU meter
P -2211-I
Figure 1-Type 76-82 Consolette with Door Open IB-24454

2
attenuator controls, switches, and other controls
are mounted on a slanting front panel. An arrange-
ment of switches makes it possible to use the VU
meter to check the condition of the tubes in the
program channel.
The 76-B2 and 76-B4 Consolettes are similar in
performance and operation and the instructions for
installation and operation apply to both types
unless otherwise specified.
The top of the Consolette may be opened to
inspect and service the Radiotrons and relays or
the entire upper section, which is hinged at the
back, may be lifted to expose the terminal boards
and the bottoms of the mounting plates. As may be
seen in figure 2, three terminal boards are provided
for external connections. These are mounted on
the bottom section of the chassis and are accessible
when the upper section is lifted. The terminal
boards are arranged so that the low-level audio
terminals are separated from the high-level audio
terminals and the power leads.
Five rubber -cushioned mounting plates are lo-
cated on the hinged upper chassis as follows
(left to right):
a. Relay Mounting Plate, on which are mounted
three relays and their associated equipment. Two
terminal boards, on which connections are made to
change over from two- (or three-) studio operation
to single -studio operation are mounted under
this plate.
b. Monitor Amplifier Mounting Plate, on
which are mounted the components of the monitor
amplifier and the monitor amplifier booster stage.
c. Line Transformer Mounting Plate, on which
are mounted the two line transformers and asso-
ciated resistors.
d. Preamplifier Mounting Plate, on which are
mounted the four preamplifiers.
e. Program Amplifier Mounting Plate, on
which are mounted the components of the program
amplifier and the program amplifier booster stage.
ASSOCIATED EQUIPMENT
The additional apparatus required for operating
this equipment will be determined partly by the
particular installation, depending on the number of
studios and their arrangement. The installation
described in this book is designed to fulfill, as
completely as possible, the average requirements of
the type of broadcasting station for which the
Consolette is designed. These instructions will also
serve as a guide to the customer whose installation
is not exactly as described in these pages.
The associated equipment described below, or
its equivalent, will be required for a complete
installation.
Microphones
The Consolette is normally used with two micro-
phones in each of two studios, a fifth microphone
(for announcing) in the control room, and if
desired, a sixth for an announce or transcription
booth. Terminals 9 and 10 and 47 and 48 may be
connected in parallel if the same microphone is
used for control room announcing and talk -back.
The RCA 44-BX, 74-B, MI -6203-B or 77-D ribbon-
type microphones are recommended for program
pickup, the RCA Type 88-A Pressure Microphone
for control room announcing, and the RCA MI -
6226 Aerodynamic Microphone and MI -6227
Table Stand for the talk -back circuit.
Microphone Stands
The quality and type of stands required will
depend on the number and type of microphones
used. The most suitable program -type floor stand
for use with all the above mentioned microphones
is the RCA Type 90-A. Lower priced stands such
as the KS-lA and MI -4068-D are also available.
The Type 91-A Announce Type Desk Stand
(MI -4058-C) should be used with the 44-BX
microphone only, and the 91-B Desk Stand (MI -
4092 -C ) with the other microphones.
Transcription Turntables
The RCA 70-C2 Transcription Turntables are
recommended for the transcription booth or con-
trol room installations. They may be used with the
Type 72-D or 72 -DX Recording Attachment.
Recorders
If the highest quality recording equipment is
desired, the 73-A or 73-B Deluxe Recorder is
recommended. Suggested recording setups and
connection information are shown in figure 4.
Recording Amplifiers
The Type BA -4B or 82-C1 Recording Amplifiers
are recommended for driving either the 70-C2
Transcription Turntables, when used with the
recording attachment, or the 73-A and 73-B re-
corders. (See figure 4).
Loudspeakers
The RCA Type LC -1A loudspeakers should be
used in the control room, lobby, studios, and

3
Figure 2-Type 76-82 Consolette with Chassis Raised

4
listening rooms where the greatest fidelity is re-
quired. If high-fidelity reproduction is not required
for the studios and announce booth, other types
may be used instead of the Type LC -1A in these
locations.
Signal Lights and Relays
The MI -11706 series of studio signal lights are
recommended for use in the studios, announce
booth and control room. These lights are available
with the inscriptions listed below and may be
ordered to suit the purpose for which the studios
will be used.
STUDIO WARNING LIGHTS
MI -Number Inscription
MI -11706.1
MI -11706-2
MI -11706-3
MI -11706-4
MI -11706-5
ON AIR
REHEARSAL
AUDITION
STAND BY
SILENCE
The relays and additional equipment required for in
stalling this equipment are listed under Addition of Signal
Lights.
Figure 3-6 db Pad for Telephone Lines
Power Supply
The MI -11301-B Power Supply will furnish all
the voltages necessary to operate the 76-B2 or
76-B4 Consolette and its associated relay control
system. The required voltages are listed under
Technical Data and instructions for installation and
operation of the power supply are given in part III
of this book.
Conduit Terminating Box
A conduit terminating box of the type shown in
figure 7 is required to install the 76-B2 or 76-B4
Consolette. In many cases this box is made by the
electrician or manufactured on special order. In
such cases the mounting flanges may be turned
outward instead of inside as shown in figure 7.
6DB Pad for Telephone Line
When used with some types of lines, a 600- to
600 -ohm pad (MI -4171-29) should be connected
between the output terminals of the Consolette and
the telephone line jacks to permit the Consolette to
operate into a constant impedance at all times.
The resistors for a similar pad may be ordered
as follows:
a. Resistor, 100 ohms RCA stock number
34765 (4 required )
b. Resistor, 400 ohms RCA stock number
30498 (2 required )
The resistors should be mounted in a rack or wall
box as described below and connected between the
600 -ohm Line Out terminals of the Consolette and
the telephone line jacks as shown in figure 3.
BR -84 Rack or MI -11500 Wall Box
The 6 db telephone pad described above as well
as the line jacks and line equalizers may be mounted
in an MI -11500 Wall Box or on a type BR -84 Rack
if more space is required. The MI -11500 Wall Box
will accommodate up to four MI -4645-A (Type
33-A) or six MI -4646-A (Type 33-B) Jack Panels
and one MI -4162 (Type 56-E) Line Equalizer.
Radiotrons
The types and numbers of Radiotrons required
are listed under Technical Data.
Wall and Floor Outlets
Wall and floor outlets for microphones, signal
lamps, loudspeakers, and turntables are shown in
the typical conduit layout in figure 11. Recom-
mended outlets and boxes are listed in the drawing.

5
CONSOLETTE 120^
(41 EXTERNAL
RECORDING
AMPLIFIER42
TYPE BA -IA
z OR BA -2A 1;
-BOOSTER o
AMPLIFIER
120"
REMOVE GROUND ON PRIMARY
OF INPUT TRANSFORMER
OF TYPE BA -2A AMPLIFIER.
TYPE BA -2A AMPLIFIER
CONNECTED FOR 250" INPUT
AND 600 ^ OUTPUT.
CONSOLETTE 120 -11-
41 0--4AA/1--0 0
EXTERNAL
RECORDING
AMPLIFIER
"PC
L
1
TYPE BA -4A AMPLIFIER
VOLUME CONTROL
"Bn
TYPE BA -4A
AMPLIFIER
42 0--ANV--o 0
120 "
REMOVE GROUND ON CENTER TAP
OF INPUT TRANSFORMER
OF BA -4A AMPLIFIER.
TYPE BA -4A AMPLIFIER
CONNECTED FOR 250 " INPUT
AND 15" OUTPUT.
TYPE BA -4A
-(30ND.AMPLIFIER
TYPE BA -4A AMPLIF ER
CONNECTED FOR 250." INPUT
AND 15" OUTPUT.
RECORDER
RECORDER
120^ RESISTOR - RCA STOCK NO. 30199
560 a RESISTOR - RCA STOCK NO. 5164 P -1743I3
Figure 4-Suggested Recording Setups
PN-3 V.U. METER PK-I
orbO "616-4,7, -6 6
PK-4
OVERRIDMaRECCRO
N-9
noes0MONITOR MOTE
PRO
TURK CHEOt VI. CONTROL 677
0 067600
TT ?12345 6
ia
0 0 On9u9pu0 00
T
*1 It2 Its3 K-4 K-5 Ki K-13 ----PK-2
LINE OUT
A)33 AL33P Ar-CmP AcCMP A606 ASP ENG cCo REG
000tEmra MASTER
J -I P-2 K -I0
MIXERS
K-7 P -I
P-170505-3
Figure 5-Front Panel Layout

6
OUTLINE S.
MOUNTING
DIMENSIONS
FOR MI-
NO.1 I 702
RELAY 01
"A; 'cc
17
2 HOLES FOR
NO. 6 SCREW
ALL BOX
TWO MI -11702 RELAYS MOUNTED IN A 6 X 6 X4 STEEL CABINET. MI -11702 P-170515-1
Figure 6-Relay Mounting Cabinet
CONSOLETTE
JUNCTION BOX MAY
BE SET IN WALL
OR FLOOR AS SHOWN.
NOTE: CONDUITS MAY
CONNECT TO BACK OF
CONSOLETTE IF MORE
CONVENIENT.
MI -11813-B P-170523-3
SPACE OR
MORE FOR
RAISING CHASSIS
JUNCTION BOX TO BE ORDERED WITH ONE-
PIECE DETACHABLE COVER PLATE.
CUT AS SHOWN AND DRILL FOUR HOLES
ONE AND FIVE-EIGHTS DIA.FOR CONDUITS
TO SUIT WHEN INSTALLING.
TOP VIEW
0 0 0 0 0 0
SIDE VIEW
A STEEL CABINET
SIZE 12 X 18 X 6 IS RECOMMENDED IF
WALL THICKNESS IS AVAILABLE.
(12 X I 8 X4 CABINET MAY BE USED.)
Figure 7-Installation Diagram

7
LOCATING AND CONNECTING
EQUIPMENT
Because of the flexibility of the Consolette and its
associated equipment, suggestions only can be
offered in respect to arrangement and location of
the different units. A suggested layout is shown in
figure 11 "Typical Conduit Layout". The Consolette,
the MI -11301-B Power Supply, the talk -back
microphone, and the monitoring loudspeaker are
usually located in a control room between the
studios. Glass windows between the control room
and studios are provided so the control operator
can observe the action in the studios. The trans-
cription turntables are usually located in the
announce and transcription booth, but in certain
cases may be in the control room. The Consolette
is mounted on a desk or table, the power supply
being mounted on the wall of the room. The exact
location and arrangement of the equipment will
depend upon the architectural layout of the station
and other considerations of this nature.
Connections to 76-B2 and 76-B4 Cansolettes
All external wiring is connected to the three
terminal boards which are mounted in the base of
the Consolette. These are accessible when the
chassis is lifted. The audio terminal board, at the
right and rear of the base, has solder -type terminals.
The two power terminal blocks, with solder and
screw -type terminals, are at the left of the base. All
wiring is brought in through four 1)/4 inch flexible
conduits. Four 15/8 inch -diameter holes are pro-
vided in the back of the Consolette and there are
four similar holes in the base making it possible to
attach the conduits at either place. The conduits
extend to a conduit terminating box in the wall (or
floor) which also has four I% inch holes to which
the conduits are terminated. Conduits from the
other units of the installation are terminated at this
box and the leads pulled through to the Consolette.
Details of the conduit terminating box and the
method of installing it and the Consolette are given
in figures 7 and 8.
IMPORTANT: Shielded leads should not be cut
at the conduit terminating box. They should be
pulled through to the Consolette in a continuous
piece.
Connection information is provided by the
"Conduit List" on page 11. This table lists the
conduit sizes, number and type of leads, and the
conduits in which they run as well as the terminals
END VIEW
10s2
f
r-,
REAR
a
VIEW
-Err
r'5 DIA.8 HOLES
fanyWar _- __
I
it,-
--
i a
39x5
2211 13
1916
M1-11613-13 P-170510-2
8
Figure 8-Mounting Dimensions

8
ZERO
A DJ.
(2DB C8D8 C4DB 2DB S IDB IN C
OFF 16 I
VU V VU4VU
o REAR
0 DECK
I
0 0 VOLUME
INDICATOR
CONTROL
(REAR VIEW)
-411--
OFF
I
t
0 0
18 12 0
VU VU 8
o VU 0__4VU
L
WIRES INDICATED BY DOTTED
LINES NOT TO BE CHANGED.
OFF
--I
VOLUME
INDICATOR
ZZ
MI -11613-B M-140853- I
Figure 9-Schematic of VU Meter and Pad
to which leads are connected. For example: conduit
number 2 runs from the power line box to terminals
number 21 and 22 of the MI -11301-B Power
Supply. One pair of 600 -volt stranded, shielded,
twisted leads is required. This conduit contains the
a -c supply circuit and 1/2 inch conduit is used.
When attaching conduits, care should be taken to
avoid damaging the shielded cables of the Con-
solette. If necessary, the clamps may be loosened
and the shielded cables moved slightly when the
fittings of the conduits are added. The clamps
should then be replaced.
When shipped from the factory the Consolette is
connected for two -studio operation. It may be
connected for single -studio operation by changing
the terminal board connections as shown in
figure 10 and figure 14.
Audio Input Connections
The audio input terminals of the Consolette are
connected at the factory for microphone input
impedances of 250 ohms. Should it be desired to
use 30 -ohm microphones, the input connections
must be disconnected from the 250 -ohm primary
terminals of transformers T-1, T-2, T-3, and T-4
(terminals 1 and 6) and connected to the 30 -ohm
primary terminals (2 and 5).
As indicated in the "Schematic Diagram" figure
15, terminals 1, 3, 5, and 7 of the input should be
connected to similar terminals of RCA microphones
for proper phasing.
Line transformer T-9 and T-10 for Mixer No. 5
and Mixer No. 6, respectively, are connected at the
factory for input impedances of 600 ohms. How-
ever, the frequency response of many types of
remote lines can be improved (with or without
equalizers) by operating them into 150 ohms.
This can be done by connecting the line trans-
formers (T-9 and T-10) for 150 ohms at their
primaries as follows:
a. Remove the ground wire and the jumper
between terminals 3-A and 1-B on both trans-
formers.b. Connect 3-A to 3-B and 1-A to 1-B on both
transformers.
Audio Output Connections
The LINE OUT terminals of the Consolette are
designed to operate into a 500- to 600 -ohm tele-
phone line. When used with some types of tele-

9
(A) FOR SINGLE STUDIO OPERATION (2-1511 SPEAKERS) :
*STRAP TERMINALS I& 2: * *CONNECT T-15 AS SHOWN:
(B) FOR
21
0304
TWO STUDIO OPERATION (3-1511 SPEAKERS):
* STRAP TERMINALS 18.2,AND 33.4: * *CONNECT T-15 AS SHOWN:
9162
4
(SEE NOTE NO 1)
(C) FOR THREE STUDIO OPERATION
* STRAP TERMINALS 23.3:
01
4926304
(4-1511 SPEAKERS):
* *CONNECT T-15 AS SHOWN:
*THESE TERMINALS ARE
LOCATED ON A SMALL 4 -
TERMINAL BOARD ON THE
BOTTOM OF THE RELAY
MOUNTING PLATE.
**WHEN MAKING OR CHANG-
ING CONNECTIONS 70 1-15,
DO NOT DISTURB THE CON-
NECTIONS TO TERM1NALSNQ
I, 3, 7, 84.12 T-15 (K -90104I)
IS LOCATED ON THE MONITOR
AMPLIFIER MOUNTING PLATE.
MI -11613-B P -170519-L
Figure 10-Loudspeaker Connections
phone lines it is advantageous to insert a 6-db pad
between terminals 79 and 80 and the telephone
line. See the instructions for this under Associated
Equipment.
Connecting Associated Equipment
A complete suggested layout of the Consolette
and associated equipment is illustrated in figure 11,
Typical Conduit Layout. Arrangement of the
conduits is shown in this figure and the leads which
run in the conduits and the terminals to which they
are connected are shown in the Conduit List table.
Note that all conduits are arranged so that a -c
power leads and audio leads are not run in the
same conduit and that low-level audio leads are
not run in the same conduit with high-level audio or
loudspeaker field supply leads. Any variations on
the illustrated setup should be arranged to conform
with this practice.
Power for one, two, or three 100 -volt, 1,000 -
ohm, 10 -watt loudspeaker fields may be obtained
from the MI -11301-B Power Supply. The instruc-
tions given in this book under Power Supply should
be carefully followed. If speakers which have dif-
ferent field voltage and power ratings are used a
separate field voltage power supply unit must be
provided.
ADDITION OF SIGNAL LIGHTS
When installing signal lights in the two studios,
the relays may be connected directly to the terminals
provided on the Consolette to obtain d -c energizing
voltage. Connections for Studio, Control Room,
and Announce Booth light relays are described
below.
Studio "On Air" and "On Audition" Signal Lights
The following equipment is required to install
signal lamps in the two studios:
a. Four MI -11702 Relays and Capacitors.
b. Two mounting boxes (See figure 6 ).
c. Studio light equipment (See Signal Lights
and Relays under Associated Equipment).
The MI -11702 Relays are supplied with 0.5 mf
capacitors but these are not required for the studio
light relays since proper filtering for this circuit is
provided within the Consolette.
The relays should be mounted in metal boxes of
the type specified in figure 6, which also shows
mounting dimensions.
Mount the boxes near their respective studios and
make connections as follows:

10
CONNECTION TABLE
Terminal No. Relay Connection
124 Common terminal for studio "A"
"On Air" and "On Audition" relays
125 Studio "A" "On Air" relay
123 Studio "A" "On Audition" relay
127 Common terminal for studio "B"
"On Air" and "On Audition" relays
126 Studio "B" "On Air" relay
128 Studio "B" "On Audition" relay
Connect the a -c supply to the signal lights through the
open contacts of the MI -11702 Relays so that the lights will
be on when the relays are energized.
Control Room On Air Relay
If the control room "On Air" light is to be used,
the following equipment will be required in addi-
tion to that listed above:
a. One MI -11702 Relay and Capacitor.
b. One mounting box (see figure 6).
c. One resistor, 180 ohms, 20 watts; RCA
Stock number 17666.
d. One "On Air" light. (See Signal Lights and
Relays under Associated Equipment).
The relay should be mounted in a metal box as
specified in figure 6 and installed near the control
room. Conduits for the control room signal lights
are shown in figure 11. Relay energizing voltage is
supplied by the voltage drop across the 180 -ohm,
20 -watt resistor which is connected in series with
the high side of the relay supply circuit of the
MI -11301-B Power Supply (see figure 14). Con-
nections should be made as follows:
a. Connect the high side of the relay supply
circuit from the MI -11301-B Power Supply to
terminal number 122 instead of 118 on the
Consolette.
b. Connect terminal 118 to terminal 121.
c. Connect the 180 -ohm, 20 -watt resistor and
0.5 mf capacitor across the control room "On
Air" relay.
d. Connect the control room "On Air" relay
to terminals 121 and 122 on the Consolette.
e. Connect the a -c supply of the Control Room
"On Air" light through the open terminals of the
MI -11702 relay (marked "A" in fig. 6) so that
the light will be on when the relay is on.
Announce Booth Speaker and Signal Light Relays
The Consolette has control terminals for the
Announce Booth speaker and "On Air" Signal light
relays but does not have terminals to supply d -c
energizing voltage for them. These relays may be
installed and energizing power obtained as de-
scribed below. The following equipment will be
required:
a. One MI -11702 Relay and Capacitor.
b. One MI -11703 Relay and Capacitor.
c. One Mounting Box (see figure 6).
d. Two 180 -ohm, 20 -watt resistors.
(RCA stock No. 17666).
e. Suitable light equipment.
To obtain energizing voltage, the relays are
connected in series with the high side of the relay
supply circuit from the MI -11301-B Power Supply.
The circuit may be connected as shown in figure 13
if the Announce Booth relays only are to be used.
If this circuit is used in conjunction with the
Control Room light relay as shown in figure 14,
connect terminal 76 to terminal 122 in addition to
the connections described under Control Room "On
Air" Relay and connect the Announce Booth relays
in series between terminal 18 of the MI -11301-B
Power Supply and terminal 122 of the Consolette
as shown in figure 14.
The 0.5 mf capacitors and the 15 -ohm, 5 -watt
resistors are included with the relay kits. Note that
connected for three -studio
operation before these relays are installed. See
figure 13 for connections.
Console Signal Lights
Two plug buttons (one at either side of the meter )
are inserted in the front panel of the Consolette and
wiring is provided to permit the addition of two
signal lamp jacks. When these are used, signal
lights such as "Pre -Set" and "On Air" can be
operated from the master control room when the
Consolette is used in large studio installations.
Terminals 67, 68, 69, and 70 may be used for
external connections to the signal lamp jacks.
The following equipment is recommended:
a. 2 lamp jacks, RCA stock no. 26562.
b. 2 lamps, RCA stock no. 21332.
c. 1 lamp cap, green, RCA stock no. 17931.
d. 1 lamp cap, red, RCA stock no. 17930.
INSTANTANEOUS RECORDER
The RCA Type 72-C or 72-D Instantaneous Re-
corder, or the 73-B Deluxe Recorder may be used
with the Type 76-B2 or 76-B4 Consolette for
recording auditions, broadcasts, or other material.
Terminals 41 and 42, which must be bridged, are

11
provided for the recording connection. Two sug-
gested recording setups are- illustrated in figure 4.
The following equipment will be required for the
setup shown in figure 4-A:
a. Four 120 -ohm (stock no. 30189) resistors.
b. One Type BA -2A Booster Amplifier.
c. One Type BA -4A Monitoring Amplifier
(MI -11223) with volume control. c. One suitable Recorder.
d. One suitable Recorder.
The following equipment is
setup shown in figure 4-B.
a. Two 120 -ohm resistors
30189).
required for the
(RCA stock no.
b. One Type BA -4A Monitoring Amplifier.
CONDUIT LIST FOR TYPES 76-B2 AND 76-B4 CONSOLETTES
Note No. 1: The following list of conduits refer to the typical conduit layout illustrated in figure 11.
conduits in the figure.
Note No. 2: Terminal numbers in bold face type refer to terminals on the MI -11301-B Power Supply.
Note No. 3: Asterisks (*) indicate optional equipment shown in dotted lines in figure 11.
Note No. 4: Wires in conduits are indicated as follows:
A. MI -64 (No. 20 AWG stranded, 300 -volt, shielded, twisted, pair).
B. MI -65 (No. 16 AWG stranded, 600 -volt, shielded, twisted, pair).
C. Pair No. 14 lead covered.
Numbers refer to
Con-
duitNo. Size From To Wire Circuit Terminals
11/2 Power Box MI -11702 Relays 1-C A -C Supply A -C
21/2 Power Box MI -11301-B Power Supply 1-C A -C Supply 21 -and 22
31/2 Power Box TT -1 1-C A -C Supply A -C of TT -1
41/2 Power Box TT -2 1-C A -C Supply A -C of TT -2
5* 1/2 Power Box MI -11702 Relays 1-C A -C Supply A -C
6*. 1/2 Power Box MI -11702 Relay 1-C A -C Supply A -C
7* 1/2 Power Box TT -1 (booth ) 1-C A -C Supply A -C
8*.... 1/2 MI -11702 Relay "On Air" Light Studio A 1-C A -C A -C
9* 1/2 MI -11702 Relay "Audition" Light Studio A 1-C A -C A -C
1-B Speaker Field 19 and one side of
10 1/2 Consolette Cue Speaker Studio A studio B speaker field
1-C Speaker Audio 133 and 134
11* 1/2 Consolette Light Relays Studio A 2-A D -C to Relays 124 and 125
"On Air"
123 and 124
"Audition"
12 I/2 Consolette Microphones Studio A 2-A Microphone 1 and 2, 3 and 4
13 V2 Microphone I Microphone 2 I -A Microphone
Studio A Studio A I -B Speaker Fields. 19 and 20
1 to 101
2 to 102
14 11/4 MI -11301-B Conduit Box 7 to 107
Power Supply 4-B 8 to 108,,
9 to 109
10 to 110
22 to 112
13 to 113
1-B Relay 17 to 117
18 to 118
15 to 115
15 11/4 MI -11301-B Conduit Box 16 to 116.
4 to 104
4-B Plate Supply 5 to 105
6 to 106
11 to 111
3 to 103
14 to 114

12
CONDUIT LIST (CONT'D)
Con-
duitNo. Size From To Wire Circuit Terminals
16 None Consolette Talk -Back Microphone
17*.... 1/2 Consolette Announce Booth Relay
18*.... 1/2 TT -1 (Booth)
19* 1/2 TT -1 (Booth)
20* 1/2 Consolette
21 1/2
22 11/4
23 11/4
24 11/4
25 11/4
26 1/2
27* 1/2
28 1/2
29* 1/2
TT -2 (Booth )
TT -2 (Booth)
Office Speakers
Cord .. 1-A Microphone .47 and 48
{1-B Audio 135 and 136
2-A D -C to Relays ....75 and 76
1-C A -C A -C
1-A Audio Audio term. of TT
1-B Audio 135 and 136
Consolette 'FT -1 Audio (Control Room ) 1-A Audio 23 and 24
Consolette Conduit Box' Include in conduits 22 and 23 all wires from filaments, plates, d -c
Consolette Conduit Box to relays, audio to speakers, and station ground.
Consolette Conduit Box Include in conduits 24 and 25 all wires from microphones, turn-
Consolette Conduit Box tables, remote lines, cue lines, and line out.
Consolette n-2 Audio (Control Room ). 1-A Audio
Consolette Line Out 1-A Audio
Consolette Control Room Ann. Mic 1-A Microphone
Consolette Ann. Booth Microphone 1-A Microphone
30* 1/2 Consolette Ann. Booth Turntables 2-A Audio
31*.
32*....
33*
34*
35*
36
37
38
39
40
41*
42*....
43*
44*45*
11/4 Consolette
Remote Lines 6-A
Cue Lines 5-A
Remote
Cue
1/2 MI -11702 Booth M1-11703 Booth 1-A D -C to Relays
Relay Relay
i/2 Consolette Studio B Light Relay 2-A D -C to Relays.
I/2 Studio B Studio B "On Air" Light 1-C D -C
Light Relay
IA Studio B Studio B "Audition" Light 1-C A -C
Light Relay
1/2 Conduit Box Studio B Audio
Cue Speaker {1-13 1-B Speaker Field
1-B Speaker Audio.
Consolette Monitor Speaker ,1-B Speaker Field
1/2 Consolette Studio B Microphones 2-A Microphone
V2 Microphone 1 Microphone 2 1-A Microphone
Studio B Studio B
1/2 Ann. Booth MI.11703 Relay 1-B Audio
Speaker
V2 Ann. Booth MI -11702 Relay 1-C A -C
"On Air" Lamp
IA Consolette Station Ground 1-C Ground
1/2 Consolette MI -11702 Relay 1-A D -C to Relay
(Cont. Room )
1/2 MI.11702 Relay "On Air" Lamp (Cont. Room )..1.0 A -C
1/2 Power Box MI -11702 Relay 1-C A -C Supply
25 and 26
79 and 80
9 and 10
11 and 12
23 and 24
25 and 26
29 and 30
31 and 32
33 and 34
35 and 36
37 and 38
(39 and 40
53 and 54
55 and 56
57 and 58
59 and 60
61 and 62
D -C terminals
{126 and 127
127 and 128
D -C Term.
A -C Term. of Lamp
131 and 132
One side of studio
"A" speaker field and
one side of monitor
speaker field.
129 and 130
20 and one side of
Studio "B" speaker
field.
5 and 6
7 and 8
A -C Term. of lamp
103121 and 122
A -C Term. of lamp
A -C

TO POWER
STUDIO A
POWER LINE WALL SWITCH 8 FUSE BOX
i
12345¢7 1
`ON AIR LAMP it!, -181-13-j TWO
MH17011AUD1TON"LAMP -
CUE SPEAKER-
M1C. 1
MIC.2
ANNOUNCE AND
TRANSCRIPTION BOOTH
rMIAIT 03!
I I
IA
RELAy r401111!...j SPKR
- I
II/
11
1
1
I
1
19_i -
1,
ri
`Th !-----17-
7-`,16IC)
ITT -II T:,./
It. 011- 'A
TEL. LINES WALL
TERMINAL BOX
'ON HMI -11702T -
LAMP -- LAMP RELAY
YTSC
1BT isTJ
-32--
IN"
M1-11301-B-i
POWER 14-15
SUPPLY
(A) MI -4624 WALL RECEPTACLES IN
STANDARD OUTLET BOXES.
(B) STAND A RD FLUSH -MOUNTING
OUTLET BOX WITH COVER.
(0 STANDARD EXTENSION FLOOR BOX
WITH TELEPHONE OUTLET.
(C) STANDARD EXTENSION FLOOR
BOX WITH LIGHTING OUTLET.
NOTE: DOTTED LINES INDICATE
AUXILIARY EQUIPMENT -NOT PART OF 76-138
11
10 12
r29
!30 45
TO OFFICE -2.. 0-,
SPEAKERS
Th TO TEL. CO.
9AJX RACK
OR
DB PAD MI -11500
MOUNT IN WALL BOX
RACK. FOR SEE LINE JACKS
FIG 3 AND
EQUALIZERS
STUDIO B
4 TWO r 34 at -_:.:(3; 'ON AIR' LAMP
MH1102
-33 RELAYS 5--- Bi -AUDITION"LAMP
36
--
21
383
TO STATION
42-- GROUND
CONDUIT TERMINATING BOX
IN WALL OR FLOOR
16
TALK BACK
MICROPHONE
OTT -I
21224
CONSOLETTE
CONDUIT MAY BE BROUGHT IN REAP OR BOTTOM OF CONSOLETTE - SEE FIGURE 7 TT -2
-27
26
OO
431
1L
-4-r44
rk,
IIkJ 'ON AIR- LAMP
I
I 1rTO TRANSMITTER IF
IN SAME LOCATION
MONITOR SPEAKER B
CUE SPEAKER
MIC. I MIC 2
CONTROL ROOM
ANNOUNCE MIC. M -11613- I3 7-160434-6

ON AIR
NXXTIO
250 -It
MIXERS
MIXER 5 I KI
PG A 0
MIXER 2K2
IM311
0 CM L
ALL STUDIO LIGHTS 6 RELAYS
ARE EXTRA AND OPTIONAL.
REMOTE PRE AMP 3
O
AMP. 4
MI K3 I -O.
ER 1(4 1-0-
rn'JLAITOZROL
PGM. R MONITOR
VOL. CONTROL
01"e
--ImcoriOR Ansi
METERPLATE CuRRENTS
VU CONTROL
ro- RL I
1157,
ift RL
0- RL 3
0 LINE OUT 0 MONITOR OUT
ALL KEY SWITCHES 8 RELAYS ARE
INTERLOCKED WHERE REOUIRED FOF TALK BACK CIRCUITS.
SEE FIG. 13
FOR CONNECTIONS
MIXER 5 0- -0-- -0- -0- -0- -0- -0- LINE
INPUT TRANSFORMERS
PI( I
MIXER 6 P -C1- T9
INPUT °-1
TT 2
MIXERS
CUE °J1dTji ritj 114-1
"F C REMOTE LINES
6
OVER
RIDE
K N6 Lb.
".".-"43
O
9ISO
PK
111,_JitirteitJy),J
CUE LINES
REMOTE
(ETERNAL
RECO DING AMPLI IER
AT
MONITOR
MR

15
TYPES 76-B2 AND 76-B4 RCA CONSOLETTES
PART II
Operation
GENERAL
An overall block diagram of the Consolette,
showing controls and associated equipment, is
shown in figure 12. This diagram represents a
typical installation in which the Consolette is used
in a small station to control two studios and a
transcription booth from a single control room.
The equipment can, of course, be used for single
studio operation in larger stations.
All the controls are conveniently arranged on the
front panel of the Consolette. Figure 5 shows the
front panel layout and arrangement of the controls.
Six mixer controls are arranged in a group at the
center near the bottom of the panel. The first two
of these are associated with the two microphones
in studio "A", the third and fourth with the two
microphones in studio "B", and the fifth and sixth
with two sets of pushkeys which may be used to
select any two of six remote lines or two transcrip-
tion inputs.
Above the six mixer controls are six audition -
program switches (K-1 to K-6) which control the
input to the program and audition busses. The
first four of these control the outputs of the first
four mixers which in turn control the output of four
microphone preamplifiers for the microphones in
studios "A" and "B". A switch (ANNOUNCE
REMOTE -LOCAL) on the input of the fourth pre-
amplifier may be used to switch to a fifth micro-
phone in the control room for announcing or a
sixth remote microphone at some other point (such
as a transcription booth).
Two sets of pushbuttons are mounted in the
upper right-hand corner of the panel. These buttons
are used in conjunction with the two line trans-
formers to control the input to the last two mixer
controls (K-5 and K-6). These transformers and
resistor attentuating networks are arranged in such
a way that the remote lines and transcription turn-
tables are properly terminated and matched to the
mixing pads. Each set of pushbuttons consists of
nine buttons interlocked so that only one can be
used at a time. The pushbuttons numbered one to
six in each group are connected respectively to six
incoming remote lines, those numbered TT -1 and
TT -2 to two turntables, and the remaining button
is an OFF position.
The two sets of pushbuttons are electrically inter-
locked, making it impossible to place a single
incoming remote signal or a single transcription
turntable on both mixers at once. Number 5 mixer
and associated pushbuttons have priority over
number 6.
The outputs of the six mixers feed through mix-
ing resistors, into six PROGRAM -AUDITION
switches. When these switches are in their normal
positions, the outputs of the mixers are open while
loading resistors are connected across both the
program and audition busses.
When a PROGRAM -AUDITION switch is
thrown to the PROGRAM position, the output of
the corresponding mixer is placed on the program
bus. When the switch is thrown to the AUDITION
position the signal is placed on the audition bus.
A detailed description of the various channels of
the Consolette is given below.
Program Channel
The program bus is connected to the input of the
program amplifier which consists of a booster
amplifier and a three -stage studio amplifier. The
MASTER volume control is connected between the
booster amplifier and the studio amplifier.
From the program amplifier, the signal passes to
the LINE-OUT switch which controls the output
of the Consolette to the out -going line. The LINE-
OUT switch has, in addition to its normal (or off)
position, a regular and an emergency position
(marked REG and EMG). When the switch is in the
normal position a load is connected across the