North N-541 User manual

SERI
ES
N-541, N-542
N-546, N-547
N-551, N-552
N-556 & N-557
Telephone Sets
NORTH
TELEPHONE HANDBOOK
NORTH ELECTRIC COMPANY
553 SOUTH MARKET STRUT • GALION,
OHIO

Administrative Offices & Plant # 1
NORTH ELECTRIC COMPANY
553 South Market Street
Galion, Ohio
REGIONAL WAREHOUSES
North Electric Company,
387  Market Street,
Galion, Ohio
Telephone 2-4201
North Electric Company,
754-756 Ponce de Leon Place N.E.,
Atlanta, Georgia.
Telephones EL 6564 and
EM 2618
NORTH TELEPHONE HANDBOOK
Issue No. II
Copyright

1956
North Electric Company
Galion, Ohio U„S,,A.

TELEPHONE HANDBOOK
CONTENTS

Paragraph

Page
List of Illustrations

ii
CHAPTER 1  INTRODUCTION
Section I Description 
1

1
II Service Applications

2  1
III Optional Features 
3 
1
IV Components  4-17 
1-3
CHAPTER 2

INSTALLATION
Section I General

18-19

4
II Connections

20-27
 4-6
III Adjustment

28-30

6-9
IV Test 
31 
9
V Final Procedure

32-33

9
CHAPTER 3

MAINTENANCE
Section I Inspection

34

10
II Trouble Shooting

35-39

10-18
CHAPTER 4  ADJUSTMENT
Section I General 
40  19
II Ringers
 41-43

19-21
III Dial
 44-50  21-23
CHAPTER 5  SUPPLEMENTARY DATA
Section I Replaceable Parts List 
25-26
II Table of Color Code: Colored Telephones
 26
III Table of Ringers and Ringer-Capacitors

26-27

Page ii
TELEPHONE HANDBOOK
LIST OF ILLUSTRATIONS
Page
Fig. 1 Telephone with Housing Removed
Fig. 2 Connector Block, Terminals 5
Fig.
3 Network, Terminals
5
Fig. 4
Wiring Diagram and Table of Ringer Connections
7
Fig, 5
Superimposed Ringing, Wiring Diagram
8
Fig.
6 Cradle—switch Latch, Wiring Diagram
8
Fig.
7 Dial and Cover, Rear View
13
Fig.
8 Handset, Exploded View
15
Fig °
9 Ringer Marking 15
Fig. 10 Straight—Line Ringer
16
Fig. 11 Frequency Selective Ringer 17
Fig. 12 Cradle—Switch
18
Fig.
13
Bias Check, Schematic Diagram 20
Fig. 14
Gong Adjustment, Schematic Diagram
20
Fig, 15
Telephone, Exploded View 24

Fig. 1. N-541 Telephone, Housing Removed

TELEPHONE HANDBOOK
CHAPTER 1
INTRODUCTION
Section I DESCR1PTION
I. GENERAL
The North N-541 type telephone is a modern high gain
anti-sidetone desk set. The controlled level provides
improved quality transmission on either short or long
lines.
Section II SERVICE APPLICATIONS
2. PURPOSE AND USE
The N-541 type set is designed for all classes of
common battery manual and dial services. It is
available for any of the following ringing methods:
a.
Straight line ringing and superimposed systems.
b.
Frequency selective ringing, harmonic, synchromonic and
decimonic systems.
Section II1 OPTIONAL FEATURES
3. NOMENCLATURE
The optional features available with the North N-541 type
telephones are identified as follows:
a.
N-541 Straight hand-set cord.
b.
N-542 Cradle-switch latch and straight hand-set cord.
c.
N-546 Coiled handset cord.
d.
N-547 Cradle-switch latch and coiled hand-set cord.
e.
N-551 Superimposed ringing, straight handset cord.
f.
N-552 Cradle-switch latch, superimposed ringing
and straight handset cord.
E,
N-556 Superimposed ringing, coiled handset cord.
h. N-557 Cradle-switch latch,
'
superimposed ringing,
coiled handset cord.
Section IV COMPONENTS
4. GENERAL
There are three major assemblies: the Handset, Base, and
Housing. The components of each are identified in the following
paragraphs.
5. HANDSET
Consists of the Handle, Handset Cord, Transmitter Cup,
Transmitter, Receiver, Transmitter and Receiver Caps.
Page 1

Page 2
6. BASE ASSEMBLY
Consists of the Plate, Cradle-Switch, Desk Cord, Network,
Ringer, Dial or Dial Blank, and for superimposed ringing systems
a cold cathode tube.
7, PLATE
The formed metal plate has a heavy corrosion resistant finish.
Four large rubber feet are riveted to the base,
8. CRADLE-SWITCH
a. Consists of
a frame,
switch spring pile-up and binder,
laminated phenolic actuating card, metal actuator brazed to the
cradle switch lever, and lever coil spring.
b. Model numbers ending in 2 or 7 have a latch on
the cradle switch. This holds transmitter circuit
open until release. button is pressed. See Fig. 6.
9. DESK CORD
A three-conductor cord with green, yellow, and red coding,
spade terminals and strain-relief provisions at both ends,
10. NETWORK
The telephone set contains a network Part No.
500,084, which includes the induction coil, talking
capacitor, a 45 mf ringing capacitor, equalizing
varistors, sidetone balance impedance, and a radio
interference suppression circuit across the dial
contacts.
11. RINGERS
a.
There are two types of ringers, Straight Line and Frequency
Selective. They are single coil types. The impedance is 600,000
ohms at 1000 cps. Coils have a d.c. resistance of 7500 ohms,
b. The straight line ringer (SL) is designed to operate over
the following frequency range.
Frequency 
Voltage Required
(cycles per second) 
(low bias)
16 cps

55 volts
20 cps

50 volts
25 cps  65 volts
30 cps

85 volts
33 cps  110 volts
12, STRAIGHT-LINE RINGERS
The armature for "SL" ringers has
a biasing spring swaged in
the end near the reed. In the rest position the bias spring
holds the armature toward the right hand pole piece and the clapper
near but not touching the high-pitch gong. This is to prevent the
ringer from tapping on dial pulses.

13.
FREQUENCY SELECTIVE RINGERS
On frequency selective ringers, each armature is mechanically
tuned to vibrate at a specific frequency and responds only to the
ringing frequency for which it is tuned. The rest position of the
armature and clapper is approximately equidistant between the pole
pieces and gongs.
14.
DIAL 7 TYPE
The pulsing and off–normal springs have double contact points.
With exception of the finger–wheel, all working parts are enclosed.
Contact springs, governor and gear train are enclosed in a dust–
tight plastic cover. The dial has a modern extended number plate,
standard number card, and is mounted on a snap-in bracket.
15. DIAL BLANK
The dial blank for manual systems has the same contour as the
type 7 dial and mounts on the snap–in bracket.
16, HOUSING
The housing is of high–impact plastic with threaded inserts
for mounting on the base. A hand–hole is provided for lifting
the instrument. The plastic hand–hole cover serves as a retainer
for the two plastic cradle–switch plungers.
17. CONNECTOR BLOCK
The molded connector block has 4 threaded inserts (2 double,
2 single) fitted with machine screws. The single inserts are
equipped with a
removable strap. The block has two, three, or
four terminals available. An additional insert receives the
cover retaining screw.
Page 3

Page 4
TELEPHONE HANDBOOK
CHAPTER 2
INSTALLATION
Section I GENERAL
18.
UNPACKING
Carefully inspect the local service order to insure installing
the correct instrument. Markings on the ringer coil may be
observed through the rectangular window in the base plate. The
coil is marked SL for straight line, SU for superimposed. The
frequency in cycles per second appears on frequency selective
ringers.
19.
LOCATION OF INSTRUMENT
The telephone set and connector block may be installed in any
practical location. Positions near grounded objects such as
radiators, sinks, gas or water pipes and electric outlets are
considered hazardous. This is especially true where grounded
station protectors are placed in the line. Keep the instrument
at least two feet from neon signs, fluorescent lights and other
apparatus known to create disturbances in telephones. Power
stations require special protective measures. Areas containing
explosive gases are particularly dangerous. Avoid areas of
excessive vibration. In all cases the location should have ample
accessibility for inspection and maintenance.
Section II CONNECTIONS
20. FACTORY CONNECTIONS
The ringer, dial and network are connected at the factory.
A wiring diagram, including figs. 4, 5, and 6, is packed with
each instrumento
21. DESK CORD
The three conductors of the desk cord are color coded and
connected to the network terminals (Fig. 3) as follows: GREEN
to Ll, RED to L2, and YELLOW to K. At the connector block GREEN
and RED are connected to the outside terminals, and YELLOW to
the center (strap) terminals (Fig. 2).
22.
LINE
a.
Connect the "LINE" (tip and ring) to the outside terminals
(GREEN and RED desk cord leads) of connector block. (Fig. 2).
b.
Divided Ringing — Connect a ground wire to the center

Fig, 2. Connector Block
Fig. 3. Network
terminal (yellow lead) of connector block,
c.
Bridged Ringing - At the connector block, connect the YELLOW
lead of desk cord to the same terminal as the GREEN lead.
d.
Superimposed Ringing - When shipped, phones are connected
for L2 - party. For Ll - party, reverse line at connector block.
For LI + or L2 + party the network connections must he changed in
accordance with Fig, 5.
Page 5

Page 6
23. NETWORK CONNECTIONS
The wiring diagram (Fig. 4) illustrates the proper connections
for the various service applications. When replacing the ringer,
network, dial, handset, handset cord, or desk cord, refer to the
wiring diagram.
24. RINGER CONNECTIONS
a.
The ringer has two color coded leads, one RED and one BROWN.
b.
Straight—Line and Frequency Selective Ringers — The straight-
line, 16, 16-2/3 and 20 cycle ringers use the ringing capacitor
built into the network. Connect RED lead to L2 and BROWN lead
to A of network. The 25 to 66-2/3 cycle ringers are equipped with
a capacitor, suitable for their frequencies, wired in series with
the RED lead, Connect RED lead to terminal L2 and BROWN to terminal
K of the network.
c.
Superimposed Ringers - The superimposed ringers are straight—
line ringers. The ringing circuit includes a cold
cathode tube. The wiring diagrams, Fig. 5, shows the connections
for "L2 (—)" and "L2 (+)" parties. For "L1 (—)" and L1 (-0" parties,
use the same connections and reverse the line (tip and ring) at the
connector block. When shipped, phones are connected for L2 (—)
party.
25. CRADLE—SWITCH LATCH
The cradle-switch latch holds the slate lead contact of the
cradle—switch open until the latch is released. The wiring diagram
(Fig. 6) shows the dial and cradle-switch connections related to
latch equipped telephones.
26. DIAL
The type 7 dial has four color coded (Blue, Green, and two
White) leads. Changing from manual to dial requires connections
to network, Transfer SLATE lead (cradle—switch) from RR to F.
Connect WHITE leads (dial) to GN and R. Connect BLUE lead .to F
and GREEN lead to RR. When cradle—switch latch equipped telephones
are used, the wiring diagram (Fig, 6) shows the changes required
in the related dial connections,
27. DIAL BLANK
Manual service desk sets are equipped with a dial blank. These
instruments have the SLATE lead (of cradle-switch) connected to RR
on network.
Section III ADJUSTMENT
28. STRAIGHT-LINE RINGERS
Only minor adjustments may be required on the type instrument

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
TABLE OF RINGER CONNECTIONS
COND. CONNECT BROWN RINGER
FREQUENCY 
MFD. LEAD TO TERMINAL
SL, 16, 16-2/3, 20  .45 
A
25

.27 P82
30, 33-I/3  .18 Cond.
40, 42, 50 
.10 Equipped K
54, 60
 .07 On
66, 66-2/3

.05 Ringer 
K
SU

See Fig. 5
NOTE-2 For manual service replace dial with dial blank and
transfer slate lead from F to RR.
NOTE-3 For bridged ringing, connect yellow line cord lead
to L1 at wall terminal block.
Fig. 4. Wiring Diagram and Table of Ringer Connections
listed on the service order.
a. Ringer Tapping - Tapping of the ringer, during dialing is
sometimes encountered on bridged ringing systems. The ringer is
less likely to tap if the positive (+) side of line is connected
Page 7

L2(-) PARTY
L 2(4) PARTY
G
LI
-0 RR
RW
Page 8
FOR LI (--) OR LI(4-) PARTY, REVERSE LINE CONNECTIONS
AT WALL TERMINAL BLOCK.
Fig. 5. Wiring Diagram Superimposed Ringing
LINE CORD
NETWORK
FOR MANUAL SERVICE REPLACE
DIAL WITH DIAL BLANK AND
TRANSFER RED-WHITE LEAD
FROM LI TO RR.
DIAL 
SWITCH
*THIS CONTACT HELD OPEN UNTIL LATCH IS RELEASED
Fig. 6. Wiring Diagram Cradle-Switch Latch
to (Green lead of desk cord) terminal L1 of network assembly.
Reversal of the line at the connector block may eliminate tapping'.
If this fails, increase the bias as outlined under "Bias-Spring."
b. Bias-Spring -
Two bias-spring positions enable the ringer to
meet widely varying line conditions. As shipped from the factory
the spring is in the low-bias position shown on fig. 10. To
increase the bias, remove the housing held to the base by two screws.
With a very small screw driver, or pencil, CAREFULLY move the bias
spring to the high bias position underneath the "L-shaped" portion
of the retainer. Replace the housing and check operation of the
ringer.

29,
FREQUENCY SELECTIVE RINGERS
The position of the gongs is the only adjustment necessary on
these ringers. NO OTHER ADJUSTMENTS SHOULD BE ATTEMPTED 1N THE
FIELD.
30, RINGER CUTOFF
Ringer cutoff can be accomplished at the connector block.
a. On divided ringing systems remove the jumper between the
"YELLOW" lead of desk cord and ground (center screws of connector
block),
b.
On bridged ringing systems remove "YELLOW" lead from green
lead terminal and connect to center terminal of connector block.
Section IV TEST
31. GENERAL
Check the service order specifications and perform operation
tests in accordance with local practices. The universal testa
are ringing, dialing, transmission, reception, directory number,
and freedom from noise.
Section V FINAL PROCEDURE
32. NUMBER CARD
Remove the number card, protector and retainer ring from
glassine envelope. Mark directory number on card. Place card
and protector on retainer disc with the two cut—out sections
over the locating extrusions. Place flange of ring over top
edge of retainer disc and place both thumbs on face of ring at
top. Maintain pressure on thumbs and move thumbs downward on
face of ring. With final pressure at bottom, ring snaps in
place.
33.
INSTRUCTION TO SUBSCRIBER
Demonstrate the correct use of the dial to the subscriber.
Call attention to the directory number and obtain a ring—back
for subscriber to identify ringing. Instruct subscriber regarding
special numbers (applicable to the area) for Information, Long
Distance, Emergency, and Repair Service,
Page 9

Page 10
TELEPHONE HANDBOOK
CHAPTER 3
MAINTENANCE
Section I INSPECTION
34. ROUTINE CHECKS
The suggestions outlined will materially aid the maintenance
and repairmen in performing their routine inspections.
a.
Handset Assembly — Check handle, transmitter and receiver
caps for cracks or breaks. Listen for noisy transmitter. Make
sure all connections and caps are tight.
b. Housing and Plungers — Check the following; housing for
cracks or breaks, plungers for free operation and mounting screws
of housing for tightness.
c.
Dial or Dial Blank — Make sure dial or dial blank is
securely mounted. Check dial for operation.
d.
Number Card — Check number card, window and retainer ring
for legibility, tightness or damage.
e.
Desk and Handset Cords — Check cords for cracks, splits or
damaged conductors.
f.
Connections — Place receiver to ear, check for loose
connections by tapping handset and housing. Shake desk and
handset cords.
I. Ringer — Check ringer operation by obtaining ringback,
h. Transmission and Reception — Check by calling wire chief,
repair service, or other designated party.
Section II TROUBLE SHOOTING
35. GENERAL
The troubles encountered in many cases are the result of
incorrect installation or misplacement of wires when housing is
removed for inspection. The table facilitates location of the more
common faults and indicates the recommended corrective measures.
36. FIELD MAINTENANCE
Field Maintenance should be limited to the adjustments covered
by paragraphs 28, 29, and 30; routine checks par. 34 and trouble
shooting remedies par. 37.

CAUT1ON: NO ADJUSTMENT SHOULD BE MADE EXCEPT WHERE TROUBLE EX1STS.
37. TROUBLE SHOOTING TABLE

FAULT
(Bell continues
to ring with
handset removed
from cradle.)
Bell rings but
cannot hear
anyone one line.
No dial tone.
Page 12
CAUSE
Open circuit in net-
work induction coil.
Cradle-switch line
contacts do not close.
Open circuit in hand-
set cord or receiver
unit.
Off-normal dial
contacts closed.
Pulse contacts open.
REMEDY
Replace network (par.
39-n).
Replace telephone set.
(See foot note 2.)
Replace handset cord
(par. 39-g) or receiver
unit (par. 39-a).
Replace dial.
(See foot note 3).
Replace dial
(See foot note 3.)
Open circuit in
network.
Cradle-switch line
contacts do not close.
Open circuit in desk
cord.
Replace network.
(Par. 39-n).
Replace telephone set.
(See foot note 2).
Replace desk cord.
(Par. 39-m)
Cannot break
dial tone.
Loud clicks in
receiver while
dialing.
Called party
cannot hear.
Pulse contacts do not
open.
Dial filter capacitor
short-circuited.
Ringer capacitor
short-circuited
(bridged ringing).
Off normal dial
contacts do not close.
Loose connection.
Open circuit in
transmitter unit.
Replace dial.
(See foot note 3.)
Replace network (par.
39-n).
Replace ringer capacitor
(See foot note 1).
Replace dial.
(See foot note 3.)
Check connections (Fig. 4
wiring diagram).
Replace transmitter unit,
(Par. 39-b).
Open circuit or loose
connection in handset
cord.
Check connections or
replace handset cord,
(Par. 39-g).
High sidetone

Network sidetone

Replace network.,
level.

impedance defective.

(Par, 39-n).

Foot Notes:
1.
Replacement .45 mf capacitors are available as part 564827.
See Ringer Capacitor par. 39-k.
2.
Cradle-Switch may be replaced at the exchange. See Par. 39-o.
3. Off-normal and pulse contact springs may be replaced at the
exchange. See par. 48-e.
Fig. 7, Dial and Cover, Rear View
Page 13

Page 14
38. LUBRICATION
a. The dial mechanism is the only part of the N-540 telephone
which may need lubrication. Oil should be sparingly applied.
Perform dial lubrication at the exchange.
CAUTION: Only dial oil supplied by North should be used.
A 2 oz. bottle of this oil is available as Part No. 567472.
b. In certain atmospheres dial bearings become quite gummy,
due to absorption of the oil by sulphate and sulphide compounds.
These are formed when minute particles worn from bearings are
exposed to sulphur in the air. When these adverse conditions
exist, the dial should be disassembled and cleaned with a deposit—
free safe solvent. Re—oil after cleaning.
c. Normal lubrication points are the end bearings on governor
shaft and intermediate shaft, clutch springs, and the lift stud
on the drive gear. The center shaft, except under the adverse
atmospheric conditions, will not require re—oiling. Reserve oil
is contained in the oil groove.
CAUTION: Be extremely careful. Governor shoes and drum must
be oil—free for proper functioning.
39. REPLACEMENT OF COMPONENTS
The following paragraphs briefly outline the procedure for
replacement of the components or assemblies.
a.
Receiver Unit — Remove cap, remove unit from handle, loosen
screws and disconnect wires. Replace in reverse order,
b.
Transmitter Unit — Remove cap, lift out transmitter unit.
Replace in reverse order.
c.
Transmitter Cup — Remove transmitter unit, lift out cup.
Loosen screws and disconnect wires. Replace in reverse order.
d. Handset Handle — Remove receiver unit, transmitter unit,
transmitter cup. Loosen strain—relief screw and remove handset
cord from handle. Replace in reverse order.
e. Housing — Remove handset from cradle. Loosen two screws
(one at front, one at back edge) under base plate. When housing
is free lift off. Replace in reverse order.
f.
Plungers — Remove housing and turn upside down. Remove
screw of hand—hole cover. Lift out cover. Lift out plungers.
Replace in reverse order.
g. Handset—Cord — Remove receiver unit, transmitter unit,
transmitter cup, handset handle and housing. Disconnect
handset—cord leads from terminals GN, B, and R of network.
Remove strain—relief hook—retaining screw from base plate.
Remove handset—cord. Replace in reverse order.

Fig. 8. Handset, Exploded View
h Dial - Remove housing
Disconnect dial-leads from
terminals F, RR, GN, and R
of network. Grasp two front
feet of dial bracket between
thumb and fingers, squeeze
lightly and release feet
from slots in base plate.
Lift dial up and remove
tongue from cradle-switch
bracket. Turn dial face
down and remove two mounting
screws. Remove dial from
bracket. Replace in reverse
order.
i. Dial Blank - The dial
blank is mounted on the
bracket by two screws (the
same as the dial).
NOTE: Mounting screws
hold plastic dust-cover
on dial. Replace screws
to retain cover in place.
Fig. 9, Ringer Marking
Page 15