3M

Some really random text about 3M's traffic division here. (Also, be sure to reference that they made a bi-modal, time-programmable sign, too!)
This page is a work in progress!

Products

Programmable Visibility Signals

Vehicle Signals (12")

M-123 Programmable Visibility Prototype Signal

Early version of the M-131. It is believed, at this time, that the first PV signal was identical to the well-known M-131 signal, with some refinements done to the casting when it was redubbed the M-131 and expanded in the product line. M-123s were sand-casted, and somewhat heavier than M-131s. M-123s generally didn't have visors equipped, as it wasn't the standard for them. The rear lamp housing was conical-shaped, unlike the M-131's more faceted door. M-123s didn't have a means of securing the fresnel lens, so lenses were prone to falling out if the door was opened. The M-123's doors had 2 hinges on top and 2 wingnuts on the bottom, similar to some pedestrian signal housings.

M-131 Programmable Visibility Signal

3M M-131 signal

3M M-131 signal

3M 131 Marketing Photo

3M 131 Masking Demonstration

Info I have saved on 3Ms, feel free to rip apart, correct, reword, whatever. -Pyth 3M, the same company that makes well-known everyday products such as Scotch tape, entered the traffic control industry in 1969 with High-Visibility signals. These lights were unlike any other at the time in both design and operation. They featured PAR-46 lamps in the back of the signal, with an opening back housing that had an auto-disconnect to prevent electrical shock. This light would shine through multiple layers, which helped prevent a condition known as the 'sun phantom effect', where a signal would appear to be lit in all 3 indications during sunrise or sunset. The unique signal build also offered 'programmable visibility', where a technician could mask off parts of the road the signal faced so only certain lanes or areas saw the signal indication, while masked off areas saw the signal as off or very very dimly lit. At a time before louvers, this was very helpful in congested or crammed areas where drivers could be confused or overwhelmed by the number of signals lit. This unique feature came at it's own cost, however. A 3-section M-131, the most common model, weighs in at around 65 pounds, whereas the average 3-section 12" head comes in at around 40 pounds. Also, as mentioned, the M-131 uses PAR-46 lamps, which have much shorter lives than the average signal bulbs, and cost considerably more each. The PAR-46 bulbs also get incredibly hot after being on for a while, which is an inconvenience for collectors and field technicians. McCain produces a near-identical line of High-Visiblity Signals as well, which are understood to cost less but weigh around 80 pounds per 3-section head. 3M stopped producing this line in 2007, due to decreasing orders. Many collectors like to have at least one of these signals due to their unusual design.

LED inserts are offered by third party manufacturers (ElectroTech), but they usually require the removal of the photocell dimming unit to ensure proper function. --To Be Edited--

Front Door

The front door was always flat-black in color from the factory. The door itself was a simple square ring with screw-holes for the visor, hinges, and an inset for the lens to fit in. The weather-tight seal was produced by the lens gasket itself, sitting in the door.

Back Door

The back door held the bulb socket and basic wiring, including the plug for electrical connections. In earlier models, only two connections were made (the bulb only uses two of the three prongs) for the circuit, but in later models, three wires were used, the middle connection for a larger-wattage resistor for the dimmer. Opening the back door also gives access to the diffuser lens and back of the masking lens, which is used to mask off areas where drivers shouldn't see the signal.

Main Housing

The main housing contains the dimmer, light shield, wire terminals, and access to the masking lens.

Lenses

The lenses on a 3M are square and have a fresnel pattern to them. This 'enlarges' the view to the driver, effectively enlarging the point of the visible mask/diffuser lens to the driver. Lenses are two-piece, with the fresnel pattern on the inside of the inner (when mounted in a signal) piece. Masks provided the symbols on the lens, and was either printed on the outside of the inner lens, or both on the outside of the inner and outer lens. Known masks include:

• None - A square when lit up. (Used in Canada for Red?)
• Ball - A round ball. Red, Yellow, Green.
• 90 Arrow - An arrow that would point Left or Right, or Up or Down. Red, Yellow, Green, Clear.
• 45 Arrow - An arrow at a diagonal that could point Up Left, Down Left, Down Right, Up Right. Red, Yellow, Green. Later diagonal arrows were created using lenses that had already been masked with a ball. These are noticeable when studied - you can see the raise of the original 'ball' mask.
• M-131R - A round ball with a prism arrow. Used in the M-131R signal (see below). Green (Red?)
• Pedestrian - Pedestrian lenses, worded ('WALK', 'DONT WALK') or symbol (Man, Hand). Portland Orange, Clear. (One variant, used in a bi-modal Ped was half PO, half Clear)
• Light Rail - Bar symbol, used for light-rail, in either 90-degree or 45-degree. Clear. (Only seen in pictures?)

Older lenses were formed and have round corners, while newer lenses were made completely square, and then had the corners trimmed off to fit into the door. All doors had a number stamped onto the outer side of the lens, possibly a production run number, while all lenses have numbers engraved onto the inner of the mold, possibly showing part number or revision of the fresnel design.

Production Changes

Some design issues were changed over the course of production. An incomplete list includes:

• Dimmer - The dimmer and associated wiring was changed to support a larger-wattage resistor, housed in the back door. The dimmer, PCD-111 was changed to a PCD-111A.
• Cast Mold - The mold for the housing was changed a few times, and included changing the corners (around the hinges) and support ridges. The back door was changed to show 3M's new logo as well.
• Diffuser Collar - The aluminum collar around the diffuser lens was originally taller, but after early production was shortened.

Serial Numbers

All 3M signals were given a serial number. A small decal, about 1" x 2" in size, was placed on the back of the housing inside the back door. A serial number was stamped onto this decal. Many lights were given sequential numbers for each head - i.e. Red would be "100", Yellow then "101", and Green "102". There were at least four versions of the decal, with the two common being known as the 'Old Style' and 'New Style'.

A list of known serial numbers owned by collectors can be found here.

McCain Programmable Visibility Signals

The McCain PV Signal was developed in early 2000's, and many parts are interchangeable with the 3M M-131, including the Light Shield, Diffuser and Masking Lens, Bulbs (LED or Incandescent), and Wire Terminals. McCain's signal uses round lenses (overcoming one of the drawbacks to 3M's square lenses) and uses their standard 12" visors. This helps with interchangeability with other signals a municipality may have.

M-131R Bimodal (Ball/Arrow) Signal

Different views that a driver could see approaching an M-131R lens.

The M-131R signal was nearly identical as the M-131 signal body, with the main feature being the prismatic lens. The lens had the normal fresnel pattern to it, enlarging the masking lens to the driver, but then also had an arrow in a prismatic pattern within the ball area. Instead of masking where the drivers wouldn't see the signal indication, masking would simply hide the ball indication, leaving the arrow always visible to vehicles.

At a distance, the driver's view of the signal is of the unmasked section, so the driver sees the ball indication (created by the diffusing lens which is unhidden by the masking lens). As the driver nears the signal, their view of the diffusing lens changed to an area that is masked off - this view is created by the Fresnel lens. The arrow, being prismatic, catches light from lower areas on the diffusing lens that isn't masked, redirecting the light to the driver, causing the arrow to appear lit.

Because of the prismatic part of the lens, this module was intended to be mounted at a 0-degree tilt, requiring a different visor and mounting section to the other tilted heads. Because of the prismatic nature, separate lenses were made for vertical and horizontal arrows. Green lenses were only advertised to be available, to be installed in a signal with ball or arrow yellow and red units, however, a red M-131R arrow has been found in California.

Other than the lens, mounting section, and visor, the rest of the head for an M-131R is identical to an M-131 signal head.

M-133 Dual-Indication (Green/Yellow) Signal

This was a true bimodal section, as to how bimodal is typically used in this industry. This was a seperate section sold as an addon, preferrably to a M-131 signal. This section contained a single clear lens and a set of color filters. A rotissarie motor was housed in an extension off to the side of the signal and was responsible for running a set of baffles that would change the filter from green to yellow. Typically this was only used with arrows and saved some of the expense and most of the space of adding a full two sections to an existing signal. --To Be Edited--

Pedestrian Signals (12")

M-131 P.V. Pedestrian Signal

3M also marketed the M-131 signal with "Don't Walk" and "Walk" lenses as a pedestrian signal. In later years they would also offer the international U.S.-spec Man and Hand lenses. --To Be Edited--

M-132 Dynamic Pedestrian Signal

Same as the M-133 Arrow signal, but using a Don't Walk lens and selective lighting to control if a red DONT WALK message was seen or a blue WALK message. --To Be Edited--

Signal Adapters/Converters

Vehicle Signal Adapter (8")

SA-130A (Adapter attachment)

These were long extension tubes installed in place of the lense and visor of any 8" signal (a necessity as these were sold as retrofit kits and 3M never produced an 8" signal of their own). They were mini versions of the optical setup of the M-131 signal bringing the same features and capabilities to existing signals, possibly saving a city costly conversions to 12" signal heads. --To Be Edited--

Vehicle Signal Converter (12")

M-150 (Lens/Reflector System)

The 3M M-150 Lens & Reflector System was created by 3M to give regular 12" traffic signals some of the M-131 signal's features.
The M-150 is installed almost exactly like a modern LED module. The signal's original socket, reflectors & lens would be removed; the M-150 unit has all of those in it. The wires that went to the original socket are rewired to the back of the unit. It is then fitted into the door just like the lens was.
The front extended part is a dual diffusing lens (dome-shaped on the inside, cylinder-shaped on the outside). These inserts offered the High Visibility feature of the M-131 signal (having a fuller, brighter & clearer indication, compared to that of a typical incandescent signal). It did not have the Programmable Visibility feature, because the masking would have to be applied too close to the light source to have the proper effect.

DISCONTINUATION:
3M discontinued these early on, because they caused an effect called 'sun phantoming', which occurs when the sun shines through the lens and is reflected back out by the reflector, making it look like all indications are lit.

PC-310 Signal Intensity Control

Nothing is known about this device.

Signal Enlargers

Signal enlarges are attachments mounted on a signal door that expand to fit a larger lens. Around the early 60s, larger signal indications were becoming more popular because visibility was becoming a greater concern. Installing enlargers on a signal was cheaper and easier than replacing it.
3M made 3 lines of signal enlargers; for vehicle signals, round-lens pedestrian signals, and square-lens pedestrian signals. They were all reprimanded for not being built to 3M's strength & quality standards; they were made of thin, lightweight folded sheetmetal with many unsealsed slots on the corners and along the sides. They were mounted in the place of a signal's visor, using the exact same attachments.

Vehicle Signal to Vehicle Signal

This image is from the 1975 3M catalog in the document archive shows the 812 (top) & 810 (bottom) enlargers.

Diagram of SA-812 from the document archive

This is an SA-812, picture from http://www.trafficsignalmuseum.com/

These were made to convert the display of typical 8" signals to that of a 12" signal.

SA-812

Patented on December 17 1973, this enlarger unit converts a typical 8" signal indication to a 12" indication. The enlarger mounts where the visor would go on the signal's door. It is essentially a box that expands around an 8-inch lens to fit a door with a 12-inch lens.
The signal's original 8-inch lens is replaced with a glass diffusing lens. The enlarger is attached in the place of the visor using the visor's screws. It is octagon-shaped where it attaches to the door; as it extends outward, the slanted sides (which are triangle-shaped) become the corners of the square-shaped front. A square lens slides into the lens holder/front door of the unit, which has a 12" circular hole for the indication to shine through. The door then simply slides into place on the front of the enlarger.
With this setup, the light shines through the 8" lens, into the enlarger and out the 12" lens, generating a larger and more visible indication with the same amount of light and without having to replace the signal.
3M specifically noted that these enlargers would not fit Eagle Durasig signals or any TSI signals. They offered special clips needed when mounting on Crouse-Hinds signals.
The name of this product means "Signal Adaptor - 8 inch to 12 inch"

SA-810

If enlargers need to be used on two consecutive sections of a signal (for example, the 2 green indications on a 4-section R–Y–G–GA signal), there would not be enough space. The SA-812 12" enlarger extends slightly over both sections around it in order to... well, enlarge... and you would not be able to fit a second one beneath it.
That is what the SA-810 is for; it is designed specifically to fit under an SA-812. It is almost exactly the same as the SA-812, except that it bends down at the top (instead of up) to fit beneath and match the curvature of the other one. Because of the height limitation, the lens is only 10"x12". And due to that irregular size, they were only available with green left or right arrows. Horizontal arrows are the only indications that would be able to fit while remaining the correct size.
The name of this product means "Signal Adaptor - 8 inch to 10 inch"

Vehicle Signal to Pedestrian Signal

Though the 3M catalog specifically says these "are adapters to enlarge 8" vehicle signals to 12" pedestrian signals", they were most likely designed for round-lens WAIT-WALK pedestrian signals (which used the same housing as vehicle signals).

SA-812DW

This enlarger uses the same body as the SA-812 with the lens & door of a SA-912.

The name of this product means "Signal Adapter - 8 inch to 12 inch pedestrian, DONT WALK"

SA-810W

This enlarger uses the same body as the SA-810 with the lens & door of a SA-910.

The name of this product means "Signal Adapter - 8 inch to 12 inch pedestrian, WALK"

Pedestrian Signal to Pedestrian Signal

Diagram of SA-912 from the document archive's 3M 1975 catalog.
If you notice, this image has 2 mistakes; the dotted signal behind it is a vehicle signal (instead of a pedestrian signal), and the back of the enlarger has an octagon shape (instead of square).

3M 910 & 912 Enlargers. They are mounted on an Eagle Flatback pedestrian signal.

This image from http://www.stamfordadvocate.com shows a pedestrian signal with 3M 912 & 910 enlargers in Washington D.C.
The signal has since been removed.

3M 910 & 912 Enlargers

The SA-910 diffusing lens (bottom) next to a normal 9" lens (top), which it would replace.

These were made to convert the display of typical 9" pedestrian signals to that of a 12" pedestrian signal.

SA-912

This enlarger is for the DONT WALK section of a pedestrian signal. The SA-910 is for the WALK section.

The enlarger mounts where the visor would go on the signal's door. It is essentially a box that expands around a 9-inch lens to fit a door with a 12-inch lens.
The signal's original 9-inch lens is replaced with a clear or colored plastic diffusing lens. The enlarger is attached in the place of the visor using the visor's screws. It is square-shaped at both ends. A square DONT WALK plastic frensel lens with red 4½" lettering slides into the lens holder/front door of the unit, which acts as a frame for the lens. There is a lip around the inside edge of the door frame, to which the new visor attaches. The door then simply slides into place on the front of the enlarger.
With this setup, the light shines through the diffusing lens, into the enlarger and out the 12" lens, generating a larger and more visible indication with the same amount of light and without having to replace the pedestrian signal.
3M offered specific versions of these adaptors with slightly different attachments to fit Marbelite and Econolite pedestrian signals.
The name of this product means "Signal Adaptor - 9 inch to 12 inch"

SA-910

This enlarger is for the WALK section of a pedestrian signal. The SA-912 is for the DONT WALK section.

This enlarger section has a 10"x12" lens. It is smaller because it needs to fit beneath the SA-912 adaptor on a pedestrian signal. The SA-912 (DONT WALK), which is a full 12"x12", extends slightly over the WALK section. In order to match the curvature, the top of this adaptor bends downward, instead of upward like the SA-912. Other than that, they are exactly the same.
The DONT WALK indication needs to be largest because it has two lines of text, and the WALK indication only has one. In a normal signal, the DONT WALK and WALK lenses are the same size, and the WALK has blank space on the top and bottom. That extra space could be cut off and the WALK indication would remain the correct size, which is essentially what was done with these.
Like the SA-912, this adaptor is attached where the visor would go on a signal, using the visors screws. The original lens is replaced with a clear or colored plastic diffusing lens. The outer lens, a plastic frensel lens that says WALK in 4½" white lettering, is displayed on the front of the adaptor.
The name of this product means "Signal Adaptor - 9 inch to 10 inch"