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TTS
26B
Section 4
SECTION 4
CIRCUIT DESCRIPTION
4 . 1 GENERAL.
when the m e t e r i s calibrated for full s c a l e , i . e . ,
070 b r e a k .
It will be noted that the m e t e r r e a d s
4 . 2 A block d i a g r a m of the s e t i s shown in fig. 4-1
approximately
50%
b r e a k when the s e t is not
and the schematic diagram of the instrument i s
connected to a circuit and the RECEIVE switch i s
shown in fig. 4-2.
The c i r c u i t s can be divided
in the REC-B&G (M) position, and the FUNCTION
into two sections
-
the receive o r measuring
switch i s in the
SEND
AND REC position.
The
section, and the pulse send section.
A detailed
s a m e m e a s u r i n g arrangement i s provided when
description of each section is presented below.
the sending and receiving functions a r e combined
in the SEND switch and that switch i s in the DROP
4 . 3 RECEIVING AND MEASURING SECTION.
( M = B & G , E =G&O) position.
4 . 4 The measuring section provides means for
the speed o r
70
b r e a k of pulses received f r o m
loop o r E & M circuits.
The RECEIVE switch is
used to s e t up the measuring circuit for differ-ent
modes of operation on loop o r E&M c i r c u i t s .
The METER CIRCUIT switch connects' the c i r c u i t
under test to the m e t e r f o r the measurement of
pulse speed o r
70
break.
When
70
break is m e a s -
ured, the c i r c u i t under test may be connected
directly to the m e t e r o r through a m e t e r slave
relay.
The m e t e r slave r e l a y should be used for
circuits with high capacitance o r inductance which
might distort the pulse sufficiently to give an
erroneous reading when the m e t e r i s useddirectly.
4. 5 The measuring c i r c u i t includes a 4
f"
m e t e r
with a 1mA movement.
A
70
BREAK s c a l e cali-
b r ated f r o m 0 to 10070 in 170 divisions i s used to
facilitate reading
O/o
break.
The R - C time con-
stants of the m e t e r circuit have been designed to
permit proper reading of the
70
break when the
digit
0
i s dialed on an external dial.
This damp-
ing i s also sufficient to keep the angular vibra-
tion of the m e t e r pointer to within approximately
t 1 division on the m e t e r s c a l e when a pulse r a t e
-
of 10 pps is m e a s u r e d .
4 . 6
A P P S s c a l e calibrated f r o m 0 to 25 in 1 pps
divisions i s used to read pulse speed.
4. 7
A calibration control in s e r i e s with the m e t e r
p e r m i t s setting an accurate full scale reading
(i. e .
,
070 break) for battery voltages f r o m
approximately 40 to
55
volts.
4.
8
When the m e t e r circuit i s required to m e a s -
u r e the
%
b r e a k of battery and ground pulses, a
compensating network, consisting of r e s i s t o r
R30 and R29B portion of the m e t e r calibrating
potentiometer, is switched into the m e t e r circuit
to provide an a c c u r a t e reading under these con-
ditions.
It i s to be noted that when receiving
battery and ground pulses through the slave r e l a y ,
R29B, i s ganged to the m e t e r calibration control
s o that it i s automatically s e t to the proper value
4.
9
The REC E & M jack makes it possible to
receive on either the E o r M lead f r o m one circuit
without interfering with sending operations on
another c i r c u i t .
When a plug
is
inserted in the
REG E & M jack, the receive c i r c u i t s a r e simul-
taneously disconnected f r o m the E , M , LINE, .and
DROP jacks; these jacks can s t i l l be connected to
an appropriate sending c i r c u i t by the
SEND
switch.
4 . 1 0 When the s e t is used f o r measuring incoming
signals, the measuring c i r c u i t s a r e connected to
the appropriate jacks for receiving loop o r E & M
signals by the RECEIVE switch, which s e l e c t s
the d e s i r e d mode of operation independent of the
sending functions.
The connections which can
be
established for each position of the RECEIVE
switch a r e a s follows i n clockwise sequence:
a. REC B&G ON LOOP: The receive meter
c i r c u i t is directly connected to the REG
LOOP jack.
b.
REC LOOP: The battery i s furnished
through the m e t e r to the tip and ground is
extended to the ring of the REC LOOP jack
requiring only an open and c l o s u r e of a
d r y loop for a m e a s u r e m e n t .
c.
REC B&O (M): The m e t e r c i r c u i t i s
connected to the ring of the REC E & M jack
and the ring
(M)
of the D R O P jack.
d.
REC
B&G (M):
The m e t e r c i r c u i t i s
connected to the ring of the REG
E&M
jack
and the ring (M) of the D R O P jack.
e .
REC G&O ( E ) : The m e t e r c i r c u i t i s
connected to the tip of the REC E&M jack,
to the E jack, and to the tip (E) of the LINE
jack.
4. 11 I t is possible to combine the receiving and
sending operations in fixed combinations by s e t -
ting the RECEIVE switch to the e x t r e m e clock-
wise position.
This t r a n s f e r s control of the
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