| +Home | Museum | Wanted | Specs | Previous | Next |
Canon 161 Calculator
Updated 1/24/2022
The Canon 161 is an example of Canon Camera Company's (As Canon was known back then) first-generation of desktop electronic calculator. This machine is a direct descendent of Canon's first electronic calculator, the Canon 130, which was first shown in prototype form by Canon at a business machine exposition in Japan in May of 1964, and formally introduced in October of '64. Canon got into the electronic calculator business almost out of necessity. Given that Canon's main business focus (excuse the pun) was optical instruments, Canon had a very great need for performing the complex math needed for design of increasingly complex optical systems. Back in the early 1960's when all this was going on, large scale computers were available for such calculations, but such computers were very expensive, and weren't easily accessible to the engineers. What Canon needed was a device that could be put on an engineer's desk that would allow the engineer to do their own "back of the napkin" calculations needed for the design of optics. Existing electromechanical desktop calculators of the day were slow, noisy, and weren't capable of higher-level math functions without a lot of manual manipulation that could lead to errors. Canon had strong internal resources for design of electronics, and it was decided that perhaps Canon could "grow their own" electronic calculator to meet their engineers needs, and at the same time, open up a highly-lucrative new area of business for the company.
The Prominent "Brag Tag" on the Display Bezel
As early as 1962, Canon management had realized that there was a growing market for business machines, and in the five-year corporate plan created in that year, Canon executives decided that the company needed to make an entry into the business machines market. This business-driven need, along with Canon's own internal calculation need, combined to cause Canon management to create a group tasked with designing a practical desktop calculator. By early 1964, the calculator group had succeeded in building a prototype of a desktop-sized, four function, all-transistor electronic calculator that could serve the needs of Canon's own engineers, as well as provide Canon a strong entry into the rapidly developing market for electronic calculators.
The Canon 130, Canon's First Electronic Calculator
That machine was dubbed the Canon 130. By October of 1964, Canon had put the 130 into volume production and built up a sales organization, and the machine hit the market, quickly proving that Canon Camera and Instrument Co. was indeed a player to be reckoned with in the rapidly expanding electronic calculator marketplace. Within the period of a year, Canon had introduced a number of other calculators based on this first generation design. In November of 1965, the 161 was introduced, making it the Top-Of-The-Line in Canon's first generation of electronic calculators. Also included in this first generation was the Canon 151, which was essentially a cost-reduced version of the Canon 161 that omits one digit of capacity.
The Model/Serial Tag Located on the back Panel of the Cabinet
The Canon 161 is a follow-on to the original Canon 130 design. The 161 uses all of the same technology and architecture as the original 130, including the very unique Canon-designed display subsystem. The 161 differs from the original 130 by virtue of 16 digits of capacity versus the 13 digits of the original machine, and adds a single memory accumulator register that wasn't present in the 130. The exhibited Canon 161 is a fairly late example of the machine, likely produced sometime in the late 1967 timeframe, based on date codes stamped onto the circuit boards.
Canon's Unique Electro-Optical Display
The most striking thing about the first-generation Canon calculators, apart from the sheer size of the machines, is their display. The displays used on these machines are a unique display technology devised by the optical wizards at Canon expressly for use in their calculator. It is theorized, though not historically proven, that Canon devised this display technology as an alternative to using the Nixie tube gas-discharge display technology used by the other Japanese electronic calculator manufacturers at the time (primarily Hayakawa Electric(Sharp) and Casio Computer Co.) due to the fact that Burroughs Corp. in the US had invented the Nixie tube display technology, and the appropriate licensing agreements to allow Japanese companies to manufacture Nixie-type display tubes were not yet in place. It is thought that perhaps rather than potentially run afoul of licensing or patent snags with the US, Canon would simply develop their own display technology. Importing Burroughs-made Nixie tubes would have been prohibitively expensive due to shipping costs. So, Given Canon's deep experience with optics, an electro-optical type of display would be a natural alternative to using Nixie tubes in Canon's calculator. At the time, Hayakawa Electric and Casio simply used Nixie tubes manufactured by Japanese electronics component manufacturers Hitachi and Nippon Electric (NEC), and let those companies worry about any possible run-ins with Burroughs, though in the end, both the manufacturers of the copycat Nixie tubes and the calculator manufacturers that used them ended up settling up with Burroughs for all of the display tubes they had used prior to the licensing being set up (brokered through Japan's MITI(Ministry of International Trade and Industry) and the US Federal Trade Commission), and paid royalties for every Japanese-made Nixie tube used thereafter.
The display elements used in Canon's first-generation calculators is an electro-optical design, relying on tiny incandescent lamps to side-light thin panels of clear plastic that have fully-formed numerals and symbols (such as the decimal point) engraved into the surface as a series of tiny dots. These plastic panels are stacked one atop another, much like the individual digit-shaped electrodes in a Nixie tube.
Display Module Construction
Module Front
Module Back (minus rear cover)
Metal Lamp Block
Lamp Circuit Board
Digit Panel Assembly
Individual Digit Panels
Each digit panel has a tiny incandescent lamp associated with it that lights when that the numeral on the panel is to be displayed. When the tiny lamp corresponding to a given digit panel lights, the light is directed into the edge of the plastic panel. The engraved area in the plastic causes interference with the light as it travels through the plastic, with some of the light refracted out through the plane of the panel, causing the engraved dots making up the digit to light up with a yellow-white glow. The resulting digits look much like the fully formed numerals in a Nixie tube, except rather than an orange glow, the Canon display digits give off a cool yellow-white glow like that of an incandescent light bulb.
Digit Grouping Bars
Each display element contains twelve of these plastic panels engraved with the digits zero through nine, a right-hand decimal point, and a vertical bar situated to the right of the digit that is used both for grouping results into groups of three for easier reading, and for separating the multiplicand and the multiplier when performing multiplication operations. The vertical bar lights up green (a result of a green coating on the edge of the panel that the bar is engraved in) to make it contrast against the yellow-white digits and decimal points. The calculator does not perform any leading or trailing zero suppression, which seems somewhat of an omission on a machine with an incandescent lamp-based display that requires tedious replacement of a lamp if it burns out. It seems that suppressing display of unnecessary zeroes would have extended the life of the tiny lamps that light up the digits. It is suspected that Canon service technicians simply replaced an entire digit module if one of the lamps in a module burned out, as replacing the individual lamps is a very delicate operation requiring a lot of time.
Profile View of the Canon 161
Part of the reason for the physical bulk of the Canon 161 is that the display technology Canon used simply was not fast enough to allow multiplexing the display. Multiplexing significantly reduces the amount of circuitry necessary to drive a display, by time sharing the circuitry that translates the internal representation of the numbers into the form needed by the display devices, as well as the drive circuitry for the display. In order for multiplexing to work, the display elements must have the ability to turn on and off quickly, as the display is actually scanned a digit at a time, done at a fast enough rate that the human eye sees the display as continuously on. The tiny incandescent grain of wheat lamps used in the displays simply can't respond fast enough to allow multiplexing to occur at a fast enough rate such that the human operator wouldn't notice an annoying flicker as the digits are scanned. For this reason, the circuitry to drive the display in the first-generation Canon calculators using this display technology is much more complex, with individual digit decoding and driving circuitry duplicated for each of the sixteen digits in the display panel. While complex, such a display technology is very straightforward to design, which may explain why some other early calculators such as the Wang LOCI-2 and Sharp Compet 20 use a similar decoder/driver per digit design.
Canon 161 with Cabinet Removed
The electronics of the Canon 161 are quite conventional, using basic diode/transistor gates for logic functions, and flip flops for bistable elements. One aspect of the Canon machine versus other machines of similar vintage is that Canon opted to build all the working registers of the machine out of flip flops. This results in a greatly increased parts count as compared to competitors designs that used acoustic delay lines or magnetic core memory to store working registers. The machine uses a fairly standard Binary-Coded Decimal architecture, with each register made up of shift registers which circulate through a serial arithmetic unit. When calculations occur, the digits shift through the arithmetic unit and are operated upon, with the results shifted back into the appropriate register.
Two of the 161's Circuit Boards (each containing part of the accumulator) The brains of the machine are distributed
across eleven circuit boards, each measuring about 12" x 9". The boards plug
into a hand-wired (and beautifully so) backplane, with two edge
connectors on each card. The backplane is situated on the left side of
the card cage, so the cards plug in horizontally.
Some cards also have an edge connector on their top edges, mostly for the
myriad connections to the display assembly. The circuit boards are
made of phenolic, and have circuit traces only on the back side. The
wire side of the board is coated with a greenish-tinted resist.
Wire jumpers on the component side of the boards are used in cases where
the traces on the back simply can't get from point A to point B. The
circuit board layout is quite conservative, with fairly low component
density. The boards appear to have been laid out more for easy circuit routing
than optimizing density. Oddly, given the apparent lack of concern for
ease of service from a mechanical perspective, the signal names of each of
the backplane signals are clearly marked at the edge connector pins of each
circuit board. Apparently the electronics designers were more service
conscious than the mechanical engineers.
Topside Wiring Harness (Mostly connections to the Display) Mechanically, the 161 is built
nicely, with high quality heavy-gauge sheet-metal stampings and quality
fasteners. The cabinet is a complex sheet metal affair, that is quite
heavy, and probably close to bulletproof! The keyboard and display bezels
are easily removable, retained by posts that engage in friction retainers.
These bezels simply pull off, and then the two screws that hold the cabinet
in place can be removed, and the cabinet carefully lifted off. Even
though the machine is very sturdy, it's clear that the machine was
not really designed for serviceability from a mechanical perspective.
Examples of a lack of thinking of the serviceability of the machine are
numerous, including a card cage that is situated such that its impossible
to pull out a circuit board without first removing the entire card cage
from the baseplate of the machine! Another example of this is the display
subsystem -- the display elements are all hard-wired, meaning that replacement
of an individual digit unit would require de-soldering 13 wires in order
to get the defective unit out of the chassis, followed by re-soldering all
13 wires back onto the replacement unit. It also appears that the display
modules themselves are not serviceable, meaning that when a lamp burns
out, the numeral associated with that lamp will not light. While Canon's
display technology was innovative, the longevity of the incandescent lamps
surely wasn't as good as other display technologies (such as Nixie tubes)
that were available at the time.
The Power Supply Circuitry of the Canon 161 The card cage takes up most of the
real estate inside the back part of the machine. The front area of
the machine contains the display subsystem, the power supply, and
the keyboard assembly. The power supply is very straightforward, with
a large transformer converting AC line voltage to lower-voltage AC,
diode rectifier bridges converting the lower voltage AC to DC,
large capacitive filters smoothing the ripple, and transistorized
regulators keeping the voltages consistent. Amidst the power supply
is a small fan that pulls air through vents in the bottom plate of the
machine and directs it upward through the electronics and out vents in the
side and upper surfaces of the cabinet.
Detail of the Keyboard's Workings The keyboard assembly is made of
a beefy plastic chassis. The key-stalks penetrate the chassis to
actuate leaf switches that close when the key is depressed. A spring
situated under each key cap provides a positive return for the key when
the key is released. The power switch and the memory accumulator control
switch are the only two switches that don't use this leaf switch
configuration. The keyboard connects into the electronics via a meticulously
bundled cable.
Detail of the Canon 161's Keyboard Functionally, the 161 provides
addition, subtraction, multiplication, and division, along with a
memory accumulator. Addition and subtraction are performed using the
two [=] keys, one black for addition, and the other, red, for subtraction.
Multiplication problems are entered as expected, by entering the first number,
pressing the [X] key, entering the second number, then pressing the black
[=] key to calculate the result. However, when entering multiplication
problems, the display is unusual, with both the multiplicand and multiplier
on the display at the same time. This method of multiplication display
is used on a couple of other calculators in the museum, including the
Sharp Compet 20 and
Brother Calther 412.
The 161 uses a green-colored bar
to separate the multiplicand from the multiplier on the display.
For example, performing 123 X 456 would end up showing up on the display
as "0000000000123|456.", with the vertical bar indicating the multiplication.
A factor complicating this is that the machine can't display multiple
decimal points on the display at once (the decimal point logic is a '1 of 16'
decoder), so performing multiplications with numbers that contain
decimals can look rather odd on the display. For example, performing
"123.456 X 456.78" would display as "00000123.456|45678". The correct
answer is given when the [=] key is pressed, but the decimal point location
on the display only reflects that of the first use of the decimal point
key. The machine keeps track of the location of the multiplier's decimal
point internally without displaying it. Division works conventionally, with
the black [=] key displaying the result. One unusual feature of the machine
that took a bit to figure out is the [R] key. My assumption was that it
was a "reverse order" key, used to swap the operands in division problems.
This feature is very common on later Canon calculators (though it is usually
labeled "RV"), so I figured that this was the case on the 161 also, but
in tinkering with the key, it was clear that this key did not perform that
function. After a lot of experimentation, I found that this key displays
the remainder after a division is performed. Why this feature was
included isn't clear, but it is most certainly unusual. The 161
has no notion of negative numbers, results "below zero" simply wrap back
around to 9999999999999999. For example, performing 10 - 20 results
in 9999999999999990. An additional press of the [=] key will perform
a tens complement operation, which, in the case of the example, would
result in 10 being displayed.
Backplane Wiring The 161 provides a full floating decimal
point, but the functionality appears not to be complete in its implementation,
especially with regard to addition and subtraction. Any time there are
digits behind the decimal with addition and subtraction problems, all entries
must contain the same number of digits behind the decimal point, or the
result will not be correct. The machine does not appear to align decimal
points before adding/subtracting. This could be the result of a problem
with the electronics of the machine, or could have been a design compromise.
It's hard to tell without a manual for the machine. The calculator operates
perfectly otherwise, which leads me to believe that this anomaly is more a
design compromise rather than a fault with the machine.
The 161 provides a memory register
which serves as an accumulator. It appears, at least in early production
Canon 161 calculators, that the memory add and subtract keys were not
included, and somewhere along the production process, the ability to
directly add or subtract the number in the display to/from the memory
register was added. A fellow calculator collector has a Canon 161 with
a significantly earlier serial number, and it lacks the memory add and
subtract keys. Also,
an advertisement in
a publication dated October of 1967 also shows the 161 without these memory
function keys.
Late 1967 photo of final assembly & test stations for Canon 161 at Canon's Shimomaruko factory The memory register acts as an
accumulator, with separate keys for adding or subtracting the content of
the display from the accumulator (white [M] and [M] keys). The memory
register is cleared with the [CM] key, and recalled to the display via
the [T] key. A push-on/push-off key labeled [A] causes automatic
accumulation of products or quotients into the memory register when
activated, a useful feature for performing sum of product operations. On
early 161's without the white and red [M] keys, this [A] mode key was
the only way to accumulate numbers in the memory register.
Rounding out the keyboard functions,
the [C] key clears the entire machine, including the memory register.
This key must be used after powering the machine up, as when it is first
powered on, the display contains random garbage (apparently there is no
power on clear) and will behave strangely until cleared with the [C]
key. The [CI] (Clear Indicator) key clears the display (but not the
memory register), but
only after a calculation has been performed, making the key useless as a
"clear entry" function for correcting entry mistakes. The [→] key
performs two functions. First, it can be used to position a number of the
display by shifting it to the right. This can be used to trim off trailing
insignificant digits, truncating any result
to a user-desired number of digits. An example
of the use of this would be to trim the result of a division down two a few
significant digits, such as if the user performed 1/3, and wanted the
result only to three decimal places. The machine would provide
"000.3333333333333" as the result for 1/3. Pressing the [→] key
ten times would shift the least-significant digits off the display, resulting
on '0000000000000.333' when done. The [→] key can also be used
to correct numeric entry errors, by "backing out" entered numbers a digit
at a time for each depression of the key.
Red "Input Overflow" Indicator on Display Panel The 161 has an overflow indicator
on the display panel, consisting of a small incandescent bulb located behind
a red jewel. This overflow indicates input overflow only, however.
Mathematical overflow is not detected by the machine -- any result which exceeds
the capacity of the machine simply "rolls over" with no warning, which means
that the user must be vigilant when working with large numbers that could
result in overflows.
The 161 is not a fast calculator, but given
its vintage, it was a major improvement over the earlier mechanical and
electro-mechanical calculators that it was designed to replace. Addition
and subtraction complete in just a blink of an eye. Multiplication and
division times vary depending on the complexity of the calculation. Simple
multiplications take perhaps a few 10's of milliseconds. 99999999 X 99999999
takes nearly a second to perform. The machine can't deal with the 'all nines'
division benchmark to its full capacity due to limitations of the logic
of the machine. When dividing, the dividend is shifted to the left end
of the display once the divide key is pressed, and apparently the logic
that performs this shifting can't deal with a dividend greater than 13
digits in length. Entering a dividend with more than 13 digits causes an
input overflow to occur when the [÷] key is pressed. Performing
9999999999999 (13 nines) divided by 1 takes about 1 1/4 second to perform.
It appears that during calculations, the displays are dimmed, by perhaps
lowering the lamp driver voltages. Even though the displays dim during
calculation, it is possible to observe (though the incandescent lamps
used in the display are far too slow to keep up with the rate at which the
machine is churning through the calculation) some "spinning" of the digits
and the decimal point racing around. As with most early electronic
calculators, division by zero throws the machine into fits. An unusual
quirk of this machine, however, is that the machine can't deal with zero
as the dividend, as well as a divisor. Apparently the logic that shifts
the divisor over to the left end of the accumulator looks for a significant
digit (one through nine) in the most significant digit to signal the
logic to stop shifting, and when the divisor is zero, there's no signal
to stop shifting...so the machine gets hung in a loop trying to position
the divisor. While this is going on, you can see the decimal points
flitting right to left, then wrapping back around to the right as the
never-ending shifting continues. Pressing the [C] key stops the madness
and returns the machine to a sane state.
