Rotary (Pulse) Dials
I've had several visitors to
my web site ask how to remove the finger-wheel on a rotary dial telephone they
just bought on eBay, thrift store, flea market, garage sale, etc. Well,
I hope to provide some help in this area of telephone collecting/restoration
with a little help from my friends in the two clubs I belong to. Even
though touch-tone telephones became available in the mid 1960's, rotary dial
phones were still in common use in the 1980's and some die-hards are still
using rotary dial phones (like us collectors!) in the second millennium!
The irony of rotary verses
touch-tone is that rotary dials produced DIGITAL data that was used by the
equipment in the central office whereas today's modern touch-tone dials
produce ANALOG signals. All the hype about us being in the digital age
is not true of our touch-tone phones - until we get to the central office
where the tones are converted to digital format. So when someone asks
you why you have an old-fashioned rotary phone, simply tell them that it's
really very modern since it's dial is digital and not analog! Who would
be caught dead with an old analog touch-tone dial when they could have a
"modern" digital dial! :-)
Plastic Finger Wheel
If you want to know how to
remove the number card in your old rotary phone with the plastic finger-wheel,
click HERE for
instructions in GIF file format or HERE
in PDF file format (courtesy of R. Wiltfong and Steph Kerman,
respectively.)
For photos of removing the wheel from a Princess phone
(type 8FA dial), click on the following hyperlinks:
Paper clip
shown in hole of finger wheel
Close
up view of paper clip hole
Close up
view showing retainer tab dislodged from notch in finger wheel
Photo showing
finger wheel removed, exposing wheel hub
Photo showing edge view
of finger wheel notch area with tab in normal position
Photo
of finger wheel upside down to show details of notch and "retainer tab
ramp" which is what the tab slides along just prior to latching in position in
the notch when finger wheel is re-installed.
Metal Finger Wheel
I have scans of the front and back
of one type of metal number-card retainer on a model 500 set..
There is another type of
number card holder/retainer which is on a Western Electric model 302 telephone
I have. Here are some photos I took of it:
Photo showing location
of release tab of number card holder assembly
Photos of disassembly process:
Photo A -
Photo B - Photo C -
Photo D -
Photo E
Another
photo of dials that might be of interest.
A great website called the "Number
Card Archive" with lots of Dial Card scans is run by Dave Margulius.
You can probably find a number card for your telephone to print from his
collection.
I have some photos
and direct scans of various dials (mostly Western Electric). Here are
the ones I have so far:
Dial pulses consist of momentary opens in the loop; dial pulses should
meet the following standards:
Pulse rate: 10 pulses/second +/- 10%
Pulse shape: 58% to 64% break (open)
Inter-digital time: 600 milliseconds minimum
NOTE: Two pulses indicate the
digit "2", three pulses indicate the digit "3", and so on up to ten
pulses indicating the digit "0".
The following information was
provided by Steph Kerman:
"Dials used on the Western Electric
500 and 554 series were originally #7, later #9 and finally #9xA.
-
#7 has a die-cast frame and metal
gears. Number plate is attached with screws. Metal finger wheels on black dials, plastic on
colored ones.
-
#6 dial is a 3" dial for pre-500
sets using similar construction to a #7 dial. They were used in some 5302 sets
but that's not really a 500 set.
-
#9 has a stamped frame and some or
perhaps all plastic gears. # plate attached with a locking ring. Plastic
finger wheels
on all color dials as far as I know.
-
#9xA has even more plastic parts.
# plate locks on by rotation and is held by the finger stop. Plastic finger
wheels on
all color dials as far as I know. By the way, the 9xA number plate is a retrofit for #7 dials. The #9
number plate fits the #9 only.
Most 500-series set dials have 4 wires. Those intended for telephone sets with
speakerphones have 6 wires."
The simplest rotary dials have
only two sets of contacts; one set generates the dial pulse, the other set
mutes the receiver in the handset so that the load popping sounds created by
the dial pulsing contacts will not hurt the users ears. In other dials,
such as the 5H series used in the Western Electric 302 telephones, there is a third
set of contacts. What is this third set used for on
the 5H dial?
-
"It short circuits the primary of
the induction coil." - sk
-
"The extra set of off-normal form A
contacts (which are connected to the yellow leads) are to mute the speaker of
a speakerphone set up." - apb
All original material on this web site is copyrighted ©1997 - ©2005 by David Massey.
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