SECTION 304-201-101
Issue 1, January,
1957
AT8TC0 Standard
BELL SYSTEM PRACTICES
Plant Series
GRAPHICAL
DETERMINATION
REPEATING
COIL WITH
OF INPUT
IMPEDANCE
ANY TERMINATING
OF
IMPEDANCE
120D COIL
1.05
1. GENERAL
1.01
This sectioncontainstransmission
characteristics
of 12OD repeating
coils,
and chartsfor
graphically
addingthe effect
of a 120D coilto,or
subtracting
itfrom,a givenpositive
impedance.The
T network
chartsare computed from the equivalent
impedancesand image parametersgivenfordc currentsup to 100 ma.
1.02 The 120D repeatingcoilhas an impedance
ratioof 1 to 1.5,which is equivalentto a
unity ratiocoilplus an ideal1 :1.5ratiotransformer,as shown in Fig.1.This makes itpossible
to obtainthe input impedance of the 120D coil
from charts similarto those for the 1:1 ratio
coils.For a generaldiscussionof the method of
using the charts,referto Section304-200-100.
1.03 The inputimpedance2X looking into the low
side of the 120D coil, as indicated in Fig. 2,
is found by entering the appropriate chart with the
value of terminating impedance Z; = 2/3 ZT. The input impedance looking into the high side, as indicated
in Fig. 3, is given by 2X = 1.5 Z+, where Z! is the
value of input impedance obtained from the chart
for a terminating impedance ZT.
The following examples illustrate the computations for two conditions. Determine the impedance at 1000 CPS looking into (1) the low side
of a 120D repeating coil terminated in half section
22-gauge H88 cable, with a 4 mf capacitor on the
line side and a 1 mf capacitor on the drop side, and
(2) the high side of a 120D coil terminated in 600uJ
+ 2 mf with a 1 mf capacitor on the 600Q side and a
4 mf capacitor on the drop side.
Example
Looking into low side of 120D
(See Fig. 2)
(1):
Midsection
impedance
22H88,
1035–j
2,
4 mf capacitor
Terminating
Z! = 2/3
impedance, ZT + cap.
(ZT + cap.)
Freq.
Cps
——
1 mf Capacitor
Avg.
1.1
Nominal
—— mf
4 mf Capacitor
Avg.
Nominal
4.4 mf
217
690–
145
N =
1.2
+ 1 unit,
N =
2.2
Input impedance of coil, Zx
Example
735–j
–j
impedance
(2):
735–j
5
159
164
Looking intohigh side of 120D coil.
(See Fig.3)
600–j
6000 + 2 mf,ZT
–j
1 mf capacitor
Terminating
40
lo35–
From Chart 4,
Required
177
–j
1 mf capacitor
Figs. 1, 2, and 3 show, for computation purposes, the equivalent location of capacitors
normally associated with the repeating coil, and for
convenience a table of reactance
of 1 mf and 4 mf
at several frequencies is given below. The average
value of Western Electric capacitors is usually 8 to
109Io (and may be as much as 25 qo) higher than the
nominal, with proportionately
lower values of reactance.
1.04
coil.
impedance, ZT
cap.
200
–j
796
–j
723
–j
199
–j
181
From Chart 4,
N=
300
–j
531
–j
482
–j
133
–j
121
+ 1 unit,
N
500
–j
318
–j
289
–j
80
–j
72
Input impedance of coil, Z{
1000
–j
159
–j
145
–j
40
–j
36
Zx =
2000
–j
80
–j
72
–j
20
–j
18
4 mf capacitor
3000
–j
53
–j
48
–j
13
–j
12
Required impedance
1.5 z;
@ American Telephone and Telegraph Company, 1957
Printed in U.S.A.
600–j
80
159
239
.2
=
1.2
675–j
135
1013–j
203
–j
1013–j
40
243
Page
1
SECTION
2.
304-201-101
BASIC IMPEDANCE MEASUREMENTS
4
82
6
Z.c = open circuit impedance
2., = short circuit impedance
= 7.0 +j aO.001125
3.
#
C, =.0116
pf
Z*C (.05 to 3.5 V ac)
Freq.
Cps
C, = .0096
0-200 ma dc
280 ma dc
360 ma dc
200
10+j
217
6+j
195
5+j
184
300
13+j
306
9+j
280
7+j
2S9
500
20+j
495
15 +j
452
12+j
416
1000
56+j
974
48+j
895
43+j
817
1500
109 + j
1470
90+j
1380
65+j
1230
2000
175+j
1917
145 + j
1740
l18+j
1610
2500
250+j
2370
200+j
2160
165 + j 2000
3000
338 +j
2830
255 +j
2570
215 + j 2370
LIST OF CHARTS
Chart
Page
2
per Second
1
200
Cycles
300
“
“
“
2
500
“
“
“
3
1000
“
“
H
4
2000
“
“
“
5
3000
“
“
*
6
1SS 1, SECTION
c
2
6
IDEAL
TRANSF
1:1.5
1:1
1:1 5
HIGH
LOW
7
+
t
El
F-J
EQU VALENT
120D
304-201-101
FIG. I
CKT.
OF 120D
-—
II
IDEAL
TRANSF
1:1,5
2
I
HIGH
5
vALENT
CKT.
OF 120D
-.
iF
-
FIG. 2
IDEAL
TRANSF
1’1.5
1:1
.-—
*T
{3
HIGH
5
7
--
it
it
EQUIVALENT
I
1.5 %;
Zx=
LOW
.-
----
2
4
CKT. OF
120D
FIG.3
Page
3
SECTION
304-201-101
TRANSMISSION
CHARACTERISTICS
OF 120D
Miscellaneous
REPEATING
COIL
Data
Inner windings (2- 1) and (6-5), parallel wound, each 569 turns #29ES,
Outer windings (4-3) and (8-7), parallel wound, each 465 turns #25ES,
Permalloy core with 8 mil equivalent series air gap.
Impedance ratio (4-3) (8-7) to (2-1) (6-5) = 1:L5 (& 470).
Inductance of (4-3) (8-7) at 900 cps, 3V, = 0.55 hen. min., 0.90 hen.
Effective resistance of (4-3) (8-7) at 900 cps, 3V, = 450f2 max.
Inductance unbalance: (2-1 ) and (6-5) n 0.3?Z0 max.; (4-3) and (8-7) =
Equivalent Networks
12.7Q &15%.
5.5fI &15 ?10.
max.
0.370 max.
and Parameter
IDEAL
1:1,
1:1.50
4
*
1
2
2A
~A
3
8
*c
7
7
!-
0.1 -7V ac, 0-100
Cps
200
300
500
1000
1500
2000
2500
3000
ma dc in (4-3) (8-7)
Transfer
A+j
Equivalent Unity Ratio
T Network
z.,
i?c
Freq.
14
14
14
14
14
14
14
14
+j
+j
+j
+j
+j
+j
+j
+j
3
4
7
14
21
28
35
42
26 +j
39 +j
68 +j
298 + j
1020 +j
4740 +j
87500 +j
7770 –j
5
‘[
Nep.
871
1240
2060
4610
9100
19600
19500
26200
.143
.124
.106
.0866
.0721
.0554
.0256
.0171
Image Parameters
Constant
B
Rad.
tb
–j
–j
– j
–j
–j
– j
+j
+j
.112
.0902
.0632
.0326
.0174
.0063
.0135
.0544
L24
1.08
0.92
0.75
0.63
0.48
0.22
0.15
Image
Impedance
ZI
102
118
138
177
233
386
1980
1556
+j
+j
+j
+j
+j
+j
121
150
214
390
639
1056
+j 1685
–j 25
0.1 -7V ac, ?80 ma dc in [4-3) (8-7)
Freq.
CDS
200
300
500
1000
1500
2000
2500
3000
Page
4
Transfer
A+j
Equivalent Unity Ratio
T Network
z,
14 +j
14 +j
14
14
14
14
14
14
+j
+j
+j
+j
+j
+j
3
4
7
14
21
28
35
42
6 +j
15 +j
36
210
623
2000
16600
23500
+j
+j
+j
+j
+j
–j
Rad.
Nep.
Zc
737
1040
1710
3750
6980
13200
37000
44200
.154
.135
.116
.0959
.0822
.0676
.0431
.0166
Image Parameter*
Constant
B
d;
Image
Impedance
z,
–j
.123
1.34
92
+j
112
– j
–j
– j
–j
–j
+j
+j
.0998
.0700
,0366
.0210
.0106
.0009
.0387
1.17
1.01
0.83
0.71
0.59
0.37
0.14
106
124
158
198
277
683
2099
+j
+j
+j
+j
+j
+j
+j
138
196
352
561
872
1610
176
1SS 1, SECTION
INPUT
IMPEDANCE
OF 120D
REPEAT
WITH ANY TERMINATION
200
304-201-101
Chart 1
NG COIL
CPS
R
200
1
I
?
400
600
i
800
1000
1200
1400
1600
1800
2000
2200
2400
.\’ ,.
lx
,,
“Y
/
:---—:“1”’”’
<“?-””:
””””-%
“--”--“Y--’-”
-’”k”1600
800
/’”
an n
111----
.+!
.&.!-!.-
400
o
w“”’=:
‘+?’.!
—---+-–----”%”-----”-’7---’
-i-eoo
-f400
i
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
R
FOR EXPLANATION
OF USE OF CHARTS SEE SECTION 304-200-100
Page 5
1SS 1, SECTION
INPUT
IMPEDANCE
OF {200
REPEATING
WITH ANY TERMINATION
300
304-201-101
Chart 2
COIL
CPS
.U
FOR EXPLANATION
OF USE OF CHARTS
SEE SECTION 304-200-100
Page
6
1SS 1, SECTION
INPUT
IMPEDANCE
OF 1200
REPEATING
WITH ANY TERMINATION
500
304-201-101
Chart 3
COIL
CPS
R
200
x
400
800
1000
1200
1400
{600
{800
2000
2200
2400
x
—
4200
600
4200
I
*, ?
,“/
IOoc
,$
1.’
,/
$-2.5-
{000
~fi~~-i+f.-~-~--;!
j:--
1
800
,’#,3 -,-”_,
,,.
77!Z!\
—
600
‘;:
\
800
% : “ ‘_:”
++-+TM..--l‘
,’
d%.
600
40C
400
200
200
0
0
–200
-200
.+=aehz%.i+---., ,
-400
-400
– 600
-600
I...::..- Y.. : .;::./..1”...:.---1
-800
–800
//-70.2.
1
-1000
-iooo
-1200
–i200
-{400
–1400
o
200
400
600
800
iOOO
1200
1400
1600
1800
2000
2200
2400
R
FOR EXPLANATION
OF USE OF CHARTS
SEE SECTION
304-200-100
Page
7
1SS 1, SECTION
INPUT
IMPEDANCE
OF 120D
REPEATING
WITH ANY TERMINATION
1000
304-201-101
Chart 4
COIL
CPS
R
200
400
—.——
I
600
800
1000
i200
1
1400
I
t600
I
1800
2000
2200
2400
,
1
lx
-1
1000
.
1
,. .-,
1
Iv
Iv
w
!.
800
7
200
200
tl
f
0
-200
F-
-4001
“i”’
1“’”/!
a
40
i
A-200
!.
1
q –400
1
-600
&l-m”H-800
.
PPM+F+l-’2°0
I
o
...)..
....1:
200
‘:”:
’1:”.
400
1-..:[. ..’1
600
““[
800
!
~~
I
1000
1
I
{200
{400
1
{600
I
‘ 1800
i
2000
I
2200
!
2400
R
FOR EXPLANATION
OF USE OF CHARTS
SEE SECTION
304-200-100
Page
8
1SS 1, SECTION
INPUT
IMPEDANCE
OF i20D
REPEATING
WITH ANY TERMINATION
2000
304-201-101
Chart 5
COIL
CPS
R
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
x
x
{200
4200
1000
4000
800
800
600
600
400
400
200
200
0
0
-200
-200
-400
-400
-600
-600
-800
-800
-1000
+ 000
–{200
-4200
-1400
–i400
o
200
400
600
800
iOOO
i 200
1400
i600
1800
2000
2200
2400
F?
FOR EXPLANATION
OF USE OF CHARTS
SEE SECTION
304-200-100
Page
9
1SS 1, SECTION
INPUT
IMPEDANCE
OF 120D REPEATING
wITH ANY TERMINATION
3000
304-201-101
Chart 6
COIL
CPS
R
200
400
600
800
1000
f200
1400
1600
1800
2000
2200
2400
x
x
4200
fooo
1000
800
600
400
200
0
-200
-400
-600
lk--Ji$K%&J%Lm:”a.+i -800
-tooo
~}+
-420012
/-
---~ - ;
u-l--w+
I 1/ u’k+l!-
\
~,_,
“::
P+””‘-i+-+
-1200
I
-1400
WL-JR--I
i. h. .~; i.
200
[-:
:;:-T:;:: :;:.:
:“
-1400
,..
i hO”
,,-
\
0
--.30
400
600
800
1000
1200
;.w-+j-~
“
i
4400
1600
L-
t
18002000
.!”. ”’!
2200
“
“/
.“
.!
2400
R
FOR EXPLANATION
OF USE OF CHARTS
SEE SECTION
304-200-100
Page 10
10 Pages