1A3A2. When 1A4S7B is pressed, the signal is applied
voltage divider network used in adjusting NOISE
through VALUE D control 1A4AT4 to 1A3A2.
NOISE GEN ADJ button 1A4S6A is pressed, the output
d. Resistors 1A3A7R7 and R8 simulate short-
of power amplifier 1A3A4 (pin B, 1A3A4P1) is applied to
1A3A8R14 and R16 in series, and the voltage across
line and long-line loading conditions for tele-phones
1A3A8R16 is applied through 1A3A8R15 to bridge
connected to TEL LINE terminals L1 and L2. When
rectifier 1A3A8CR1 through CR4.
SHORT LINE button 1A4S7B is pressed, TEL LINE
1A3A8R8 and R9 form a voltage divider used to
terminal L1 is connected to 1A3A7R7. When LONG
measure the bias current applied to carbon
LINE button 1A4S7A is pressed, TEL LINE terminal L1
microphones. When READ MICRO-PHONE CURRENT
is connected to 1A3A7R8.
button 1A4S5F is pressed, the 1A3A3R8 is parallel-
connected with the microphone, and the voltage across
Dial Percent Break Assembly 1A3A9
1A3A8R8 is applied to 1A3A8R9 in series with meter
Assembly 1A3A9 produces a direct current that is
proportional to the make-to-break ratio of a telephone
Transmission Efficiency Assembly 1A3A7
dial switch connected to TEL LINE terminals L1 and L2.
a. When DIAL BREAK button 1A4S6L is
Assembly 1A3A7 electrically simulates physical
pressed, +24 volts from positive power supply 1A3A5
telephone line conditions for the telephone efficiency
(pin H of 1A3A5P1) is applied through contacts 7 and 8
and varistor tests.
of 14S6L to pin D of 1A3A9P1. Positive 24 volts at pin
D causes current to flow from ground through 1A3A9R7,
a. Resistors 1A3A7R1 and R2 and capacitor
CR1, R6, and R5, and from ground through pin E of
1A3A10P1, 1A3A10R11, DIAL BREAK CALIBRATE
portion of the output from power amplifier 1A3A4 to
control 1A4R18, contacts 2 and 3 of 1A4S6L, 1A4M1,
ARTIFICIAL MICRO-.PHONE terminals 1A4E4 and E5.
pin J of 1A3A9P1, 1A3A9R8, CR2, CR1, R6, and R5.
When TELE-PHONE EFFICIENCY-SEND button
DIAL BREAK CALIBRATE control 1A4R18 can be
1A4S6R is pressed, the output of power amplifier 1A3A4
adjusted for a midscale reading on 1A4M1. Capacitor
at pin B, 1A3A4P1 is applied to 1A3A7C1, R2, and R1 in
1A3A9C4 charges to the voltage across `A3A9R7.
series, and the signal developed across 1A3A7R1 is
When TEST button 1A4S5A is pressed, contacts 3 and
applied to MICROPHONE TERMINALS 1A4E4 and E5.
4 of 1A4S5A short 1A3A9R6 (pins F and L of 1A3A9P1),
and TEL LINE terminal L1 is connected through pin K of
b. Resistor 1A3A7R9 is the load resistor for -
1A3A9P1, 1A3A9CR3, pin H of 1A3A9P1, and contacts
the output of power amplifier 1A3A4 when NOISE
1 and 2 of 1A4S5A to pin L of 1A3A9P1. When .the
GENERATOR switch 1A4S3 is at LOAD. When 1A4S3
telephone dial switch that is connected to TEL LINE
is at LOAD, the output of power amplifier 1A3A4 at pin
terminals L1 and L2 (ground) is operated (the contacts
B of 1A3A4P1 is applied to acoustical output adjust
alternately make and break), L1 and L2 alternately short
1A3R11 in series with 1A3A7R9.
and open, causing 1A3A9C4 to charge and discharge.
Therefore, the current flow through 1A4M1 is
c. Resistors 1A3A7R3 through R6 simulate a
proportional, to the make-to-break ratio of the dial
telephone receiver for telephone efficiency and varistor
connected to ARTIFICIAL RECEIVER terminals 1A4E6
b. Assembly 1A3A9 also contains free-
and E7, provides dc isolation for terminals 1A4E6 and
E7. The signal applied to terminals 1A4E6 and E7 is
simulated dial pulses available at pin C of 1A3A9P1.
applied through 1A3A7T1 to 1A3A7R4 in parallel with
The period (time between pulses) which is determined
the series resistance of 1A3A7R5 and R6. When TEST
by the time constant of 1A3A9R3, C3, and dial speed
CONDITION switch 1A4S9 is at ART REC, the signal
developed across 1A3A7R6 is applied to LONG LINE
button 1A4S7A and SHORT LINE BUTTON 1A4, S7B.
When 1A4S7A is pressed, the signal is applied through
VALUE C control 1A4AT3 to meter amplifier assembly