Connectors, Stage Pin


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The most common connector in the US entertainment lighting industry, and also the oldest. Simple, right? How could something so ubiquitous, and selling for around $5 each, possibly be complicated? Well, for starters there are three basic shapes and at least four different termination methods, and nine, I think, current different manufacturers. Since the 20A 120V is far more common for live entertainment use than the 120V or 250V, 60A or 100A, we're going to concentrate this article on the "normal, regular, standard, stage pin connector."

Recent History:
When I started in lighting in the 1970s, 2P&G (aka slip, Bates, Stage Pin, stagepin, SP, GSP, Grounded Stage Pin) connectors were simple. There was one manufacturer: Union Connector, and just a couple of styles: two-pin or three-pin; cable or fixture mount; and of course gender: male and female. The gender and size are the only two items that have remained constant over the years.

Middle Earth:
When was the third, center, grounding pin added? Sometime between 1957 and 1960. The Grounded style IS in the 1960 catalog (as the 955-G below), but is NOT in the 1957 catalog.

For a number of years, as older theatres began purchasing or renting new fixtures, adapters such as these were available:

(Photo courtesy of [USER]ptero[/USER].)
The intent was to use the crimp lug to attach a ground wire to a known good ground (e.g. the conduit or raceway), but of course no one ever did that. Another common solution was to drill a 5/16" hole in the female receptacle to accept the ground pin. This practice also was frowned upon by electrical inspectors.

Dawn of time:

From a 1913 catalog on

An old Kliegl Fiber connector, cable mount, prior to 1970-ish?:

Notice the hot and neutral wires use 90° Flag terminals. There's no way to fit three straight terminals inside the plug. Note that even the round ring terminals had to be clipped to fit inside--this plug was designed for the wire to just wrap around the screw (more on that below).

A plastic Fixture Mount connector:

Notice the three channels for the three asbestos leads. At the time, all fixtures had individual asbestos leads. Notice also that the covers are not interchangeable. The spacing for the cover screws is different. Thus one had to order both Fixture and Cable Males and Females. (The Female Fixture connector would only be used on the pass-through of striplights, or when building a two-fer from asbestos wire.) Pictured is a Union Connector brand, although the cover is stamped Century, appropriate as the connector is attached to a Century 18" Scoop. Covers could, and still can today in the correct quantity, be ordered with a name or logo embossed on it. Usually this was/is the name of a manufacturer or vendor. (It has always been my goal to work in a venue with its name on every connector. All it takes is ordering a ton of connectors or covers at the beginning.)

The current manufacturers are below, roughly in chronological order. Thankfully, due to market demands, as well as this USITT document USITT, and this ESTA standard: ANSI E1.24 - 2006 Entertainment Technology--Dimensional Requirements for Stage Pin Connectors, all with mate with all others of any manufacturer. Note the document only discusses pin size and spacing, and does not encompass any electrical or ergonomic specifications.

1. Union Connector
Union has had two hourglass shaped connectors, the first, and now discontinued, allowed for the use of either pressure plates or crimp terminals. Advocates of this design favored the debatably quicker termination process of the pressure plates, which required no crimping, while detractors found that they often came loose during use, leading to a poor connection, arcing, melting, and thus ultimately failure of the connector. The current connector has done away with the pressure plates, opting instead to use either crimped terminals or ferrules. It's also worth noting that Union has switched to a combo head design for their screws, which are common on other connectors in the industry

(Thanks to the John S. Hyatt blog for these photos,

Union Connector

From Electrical Products, Stage Pin Connectors, Power Distribution Equipment :
The 2P&G pin connector manufactured by Union Connector is the standard electrical connector used in theatrical lighting. The pedigree for this device goes back to the first pin connectors made by Kliegl Bros. in the 1920's. It is sometimes referred to as a "Bates" connector. This stems from the years that Union Connector manufactured connectors for Bates Electric in California. Today, the 2P&G connector is the most widely used pin connector in the world.

2. Rosco Laboratories

Rosco US : Connectors Introduced to the market about 1982, Rosco's version, with its refined shape less susceptible to snagging, and for the first time, replaceable pins, was the biggest improvement since plastic replaced low density fibre in connector bodies. Previous Rosco connectors were labeled as "Stage Connectors, Inc.," and there are still thousands of these installed. Today all Rosco connectors feature two termination methods, as well as a beryllium copper spring insert in each female pin. The spring serves two purposes: insures proper contact by grasping the male pins tightly, and cleans the pins with each insertion/removal cycle. Also, all connectors have removable strain relief inserts to allow the connector to be used with a wide variety of cable sizes.

3. Bates/Advanced Devices/Marinco

Bates 20 Amp Male Inline: all colors & terminations | Marinco Although the name "Bates" goes back to probably the 1920s (See #1:Union Connectors above), it was dormant everywhere except Hollywood until Advanced Devices resurrected it in the 1990s. Today's Bates connector may be the most popular of all stage pins, if only by a small margin.

Note that Bates and ProPin (see below) brands appear to be identical, and likely come off the same assembly line.

4. Kupo, imported from Taiwan

KUPO - Connectors

5. Creative Stage Lighting/Entertainment Power Systems (EPS)

Entertainment Power Systems - Modular power distribution system designed for the entertainment industry.

6. PinTech

20 Amp Devices
At some prior time, PinTech also manufactured connectors with a slightly different shape.


7. TMB ProPin (no information on site other than this down-loadable PDF.)

ProPin™ Introduced about 2001, and easily confused with the Advanced Devices Bates connector.

8. Group5/Marinco (One of two manufacturers to offer a 100A 250V with pin spacing different than the 100A 125V--the other being Mole-Richardson)

Group5 20 Amp Male Inline DSS: all colors & terminations | Marinco Machined from a nearly indestructible high-density fiber, their 20A versions are significantly, about three to four times, more expensive than other brands.

9. Leviton

Leviton 20MP-CL
Some confusion exists as Leviton previously marketed Union Connector brand labeled as Leviton, but now manufactures its own.

Rectangular (No longer manufactured, but still found in theatres and rental shop inventories everywhere.) Actually the bodies, excluding the pins, are square, measuring 2" x 2" x13/16" thick.

Trapezoidal: Bates, ProPin, PinTech, Rosco, 2" wide x 3" long x 3/4" thick. The reduced width and rounded corners at the cable end is to prevent snagging on other cables and connectors.

Hour Glass: Union Connector, Group5, EPS, 2" wide x 3" long x 3/4" thick. Very similar to the trapezoidal, but with recesses for finger grips.

Other: See PinTech brand above. It is believed that this shape has been discontinued.


Crimp Terminals


A barrel shaped terminal is crimped onto the wire, before it is inserted into the back of the pin. Notice the neutral wire has been removed to better show the ferrule. If the ferrule is missing, sticking the bare wire into the pin is ill-advised, as often tightening the screw will break the strands.

Pressure Plate

The only attachment acceptable for bare wires. These sometimes have a problem with loosening over time.

Crimp directly onto pin:
ProPin and Bates offer the option of crimping the wire directly onto the pin. A manufacturer-specific crimp tool is required. Fabricators like this option as it speeds assembly, but the end-user must buy new contacts to repair or replace the connector.


Combinations of above (dual terminations).
Some manufacturers, notably Rosco and EPS, offer two methods of termination within the same connector. Other manufacturers offer two different terminations, but must be specified at time of order.

Wrap wire around screw.
At one time, was how almost all terminations were done. Rarely acceptable these days, except for short-term applications like practical wiring on a short-run show. Crimp terminals and ferrules are inexpensive and should be a staple of any theatre electrics shop.

Confusion over "shoe".
Some call Pressure Plates shoe terminals, others call the Ferrule-style shoe terminals. Best to avoid the term altogether and be more specific.

Strain Reliefs.

For 12/3 SOOW cable; for 12/3 SJO cable (as on Two-fers, Break-Ins, and Break-Outs); and for fixtures' Fiberglass Sleeving containing three 16g. wires.
Most connectors have some method for reducing the cable entrance hole if less than 12/3 cable is used. If these little plastic reducers are missing, I've found the 1" jacket scraps that remain from stripping the 12/3 are useful for enlarging the cable diameter, especially with the fiberglass sleeved conductors on modern fixtures. The use of multiple wraps of gaffers or electrical tape is not advised. Besides being a waste of tape, it tends to slide over time and becomes an ineffectual, sticky mess. If you must do this, use friction tape.

Various methods have been attempted over the years. From 1929 to 1957, Kliegl attempted to market a figure 8-shaped spring that went into a special slot on each connector. Never caught on as it was proprietary (how very Kliegl-like!)

In the late 1970s/early 80s, Union Connector introduced the Harj-Lock, to compete with the Twist-Lock connector, which was gaining in popularity.

Notice the extra hooked piece on the center pin. Pressing the button on the right side of the connector recessed this hook, which fit into most, but unfortunately not all, female sockets. The locking tab was easily broken, rendering the locking feature useless. The connector didn't last long on the market, and one seldom sees a working one these days.

Some connectors, most notably the Bates and its clones, have a 3/16" hole in them, perfect to accept a length of 1/8" tieline or Ty-Rap to fasten the line and load connectors together, or for a drywall screw to affix to a wooden member on the back of a set piece.

Probably the most prudent method is to keep the pins split, either by using a knife, CAREFULLY:

Or a special purpose tool known as a Pin Splitter, (a feature included as one of the many functions on the Ultimate Focus Tool):

If the male is loose in the female, SPREAD THE PINS--it's why they're split. Taping a loose connection just leads to arc-ing and over-heating.

Interesting trivia:
I suspect this is the patent: US Patent number: 5810624 for what became the Trixfer - Developed by Theatrix.

In order to continue to make "V" style twofers, a special strain relief, designed to accept two cable, was required. TMB's ProPin is the only manufacturer to offer such a device. From ProPin™.pdf:

More information, and links to discussion threads, in the glossary entry Stage Pin Connector. See also the wiki entry E1.24 Standard.

All photographs not credited were taken by [user]derekleffew[/user], from his personal collection.


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I have a male, rectangular, GREEN connection made to accept three asbestos wires. What's the history on it? Who made it?
I'm not positive, but I'm guessing "the green connector" was a variant by Union Connector, sometime prior to 1980. I finally found one a theatre would let me have, as it seems to have experienced melting issues, which may be why it was discontinued by the manufacturer.
I don't think I've ever seen a version for asbestos wire.
Thanks for the info, I'll try to get a pic of mine.
I have a male, rectangular, GREEN connection made to accept three asbestos wires. What's the history on it? Who made it?

I've always understood that those green pin connectors were made by( or caused to be made ) by Altman. Had many of those cook off down through the years..............
I've always understood that those green pin connectors were made by( or caused to be made ) by Altman. Had many of those cook off down through the years..............

That would make sense, as I have a number of 4.5" zooms with the connector Derek pictured (albeit unmelted)

Still curious as to the origin of my smaller bodied, 3 wire connector.
These are house brand Altman 2P&G connectors, made back in the day (70's) when the alternative pin connector was whatever the fixture/raceway manufacturer provided, OR a Union Connectors version (TMB, Bates and Rosco had not yet gotten into the market for stage pin connectors). As Altman hated paying Union for something they could source out cheaper, they had someone make the green ones. They were a good bit longer then the typical plastic Union 2P&G or other fiber versions at the time, which sometimes made life a pain when the raceway receptacle was flush to the bottom of the raceway with a 2" OD pipe mounted directly below. The shorter pin connectors would "just" fit, the Altman's would not.

They are no longer then the current crop and I cannot recall having any particular problems with melting, that wasn't typical to all 2P&G's at the time. Most good quality Stage Pin connectors are significantly more robust these days.
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Nice bit of history. Good article.
Does anyone have an example of a clear cover for a square bodied Union? They (Union) told me they made em.
Correct, it was an Altman connector.

FYI, Union offered colored covers for their connectors, and Production Arts adopted the standard of a green cover on #12 AWG cables. #14 AWG cables had a black cover.


While those of us in shops with less economic honch ( and tradition bound bosses ) had to settle for Scotch 35 tape rings to denote that sort of thing.....
Have to mention that last week I encountered a Y style two-fer made with Pintech connectors. The two female connectors had shrouds to prevent improper plugging.
Is there in fact a connector suitable for stage luminaire service in the US which *does* meet the last two requirements in your piece?
So, when picking a general-purpose connector for use at 208V, it needs to be both:

  • Rated for at least 208V and for use in a phase-to-phase application
  • Not interchangeable with connectors used at other voltages in the facility
Sounds like NEMA L6-20 to me!
I was in the booth of a high school built in 1970 testing an instrument. Popped 3 lamps before I realized the wall pocket was 220 volts. The voltage was in small writing embossed on the wall pocket cover and easily missed. I think the outlets were for high voltage follow spots that the school never had. It was probably part of the standard "School Package" that Kliegl installed at the time. Using the same plugs and outlets for different voltages was a horrible idea.

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