Rotary Dial Telephone

Listen to the sound
of the dial and bell.


Listen to the Sound
of Dial and Bell
On a Rotary Dial

Rotary dial telephone
black model 50 rotary dial telephone

Sounds of a Rotary
Dial Telephone

Rotary dial telephone
dialing sound.

Rotary dial telephone
ringing bell.

Rotary Pulse
Dial Telephone

The rotary telephone sends
out electrical pulses when
one dials out.
This is done by rotating the
dial wheel.

Lift the receiver off the hook
and wait for dial tone.
Place a finger in one of the
finger holes, rotate the
wheel until the finger touches
the finger stop.
Release the finger, the
wheel rotates backward,
sending out the pulses.

The dialing wheel returns to
its home position.

The speed of the rotating
wheel is very important,
if the dialing wheel rotates
too fast, or too slow, the
dialing will not send the
correct information to the
telephone exchange

The correct speed is about
2 seconds for the wheel to
rotate from position zero
to home position.

A seasoned telephone
repairman would sometimes
use the 1000 - 2000 count

The correct pulses are
(10.5 pps).

The speed is adjusted by
gently bending the two
flat brake springs to the
right tension.

The braking flat springs
controls the speed of a
spinning weight.

As the dialing wheel is
turning a series of electrical
opening and closing a set of

The open and close timing
of the contacts has to be
accurate so the equipment
in the central office can

A 62/38 ratio,
(62% open, 38% closed)
is necessary to send an
accurate pulse code.

This adjustment is done by
forming the contact metal

This adjustment requires
a dwell type meter to be
able to set the make-break
percent accurately.

The volume of the bell is
adjustable by loosing an
off center screw in the
center of the bell, then by
rotating the bell, the bell
is moved away or closer
to the clapper.

rotary telephone dialing mechanism

The mouth piece of the
telephone is composed of
thin metal, carbon graduals
sandwiched between the
front and back of the unit.

When a person speaks,
the top tiny metal cover
fluctuates, compressing
and releasing against the
carbon graduals.

An electrical current follows
the pattern of the voice.

This current flows is picked
up by wires and sent to the
telephone exchange
equipment, and on to the
person on the other end
of the line.

The electrical pulses are
converted back to voice,
on the receiving end.

Rotary 80 dial telephone
red model 80 rotary dial telephone


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Listen to the Sounds
of a Rotary Dial
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