The Exclusive Trimline Cord
Richard Gerber #4231
Exclusive to the early Trimline phones (AD1 base and AC1 wall base; 220A, 1220A and 2220B handsets) are the cords used by it. The cord made for the Trimline telephone had large snap in plugs that made it quicker and easier to replace or change the cord—using the proper tool—KS 16750.
 The Trimline cords can’t be used on the Princess, the 500 sets, the 2500 sets or for most other types of phones. A few exceptions were brought to my attention by Arthur Bloom. These would include the “cuckoo clock”, the 851 and 2851 wall key phones and the 830/831 and 2830/2831 series of desk key phones. Some sets were retro-fitted to hardwire. There were also some special service central office sets and test equipment using the Trimline cord. This came about after the Trimline cord had been manufactured for 10 years.
A unique invention at the time, the Trimline cord was the first and only plug-in spring and line residential and business telephone cord. There were operator plug type cords and 4 prong wall plugs to make the phone “portable”, and other cords of this type, but the Trimline cord had a different use and look. The cord started with a large plastic plug until it evolved into the small modular plug on the phones today. Soon the modular plug cord replaced the Trimline cord. When the modular cord first appeared we differentiated between them by calling them maxi and mini plugs. Only the large plug cords used on the Trimline phones (and the small number of previously mentioned sets) are rightly and properly called Trimline Cords.
The Trimline cord had its own exclusive department at Western Electric where it was manufactured. No other cords were made in the Trimline department.
There is only one Trimline cord but it has several evolving stages or types leading towards the modular cord of today. Once it became modular it was no longer an exclusive Trimline Cord. Ergo, all Trimline cords so named are large plug cords that fit only the Trimline telephones and the few exceptions.
The first Trimline cords were the H5AA and the D5AL, spring and straight (line) in that order. They have a five conductor cord in a four conductor jacket (body) and hailed as a major breakthrough by the Western Electric engineers. Usually with added conductors a cord would increase in circumference. The Trimline phone itself had to wait until the problem of squeezing five conductors and a string into a four conductor body was solved. Once accomplished, production on the Trimline cord proceeded in earnest in April of 1965AD at the Western Electric Baltimore Works.
The string helped hold the cords round shape. The paper surrounding the conductors kept the inner part of the jacket from sticking to the conductors when the ends were stripped. Later the paper was deleted, a cost savings, and the conductors were coated with silicon powder. Each step in the evolution of the Trimline Cord resulted in a cost savings with no diminishing quality or function to the cord. Soon came the H4DB four conductor cord as another option.  
The evolutionary period of the Trimline cord covered roughly the years 1965 to 1974. Production lasted a few years longer (around three?). In that span there were at least 9 distinct types of ends or plugs on the Trimline spring cord and two types of bodies (jackets). This makes well for a collection in Trimline Cords. Add the colors and a person would have a variety of collectable cords. Be aware that some of the older cords might have weakened or cracked plastic shells.
The first type of jacket (body) is a round cord about the size that was already in use on the H4CJ cord. The second kind is a flat smaller size that is still in use today.
This smaller flat cord with the large one piece plug was used on the Trimline (Type #9). The modular 2 piece plug was added almost at the same time (maybe I should have made that Type #9A). The modular cord then became the standard cord for all the phones in the Bell System and other companies as well. Start up production for the mod cord began in March or April 1974AD.
Sidebar—some people call the Trimline a Princess also. There is NO such thing. The Trimline is a Trimline and the Princess is a Princess. Western Electric never confused the two. I don’t know how that started. Yes, the later Princess phones has the mod cord as does the later Trimline. Maybe that brought about the confusion of the public between Trimline and Princess.
On all round Trimline cords with the color coded conductors, the red and green conductors had to be diagonal from each other. Otherwise there would be a feedback problem. (Likewise on the four conductor D-Station wire.)
In the manufacturing of anything there are, at times, problems that crop up in the process. A serious problem arose after two or three years of Trimline cord production. On one end of the cord the plastic shells were cracking as they were riveted. I think it was the square end of the spring cord; both the H5AA and H4DB’s were cracking. The beveled or notched end appeared okay. Supervisors, engineers, material handlers, set-up men, and women production workers spent at least two days trying to find the problem with the shells. They checked the shells, the machines, the manufacturing and other things and couldn’t find the cause. An hour after a temporary material handler came on the job of day three he noticed that the short and long rivets which were suppose to be in different bins were mixed in all of the holding bins. From the bins they were put into the riveting machines. The material handler showed the supervisor the holding bins and what caused the shell cracking problem and saved the company from further expense. I know this incident is true because I was that material handler.
In another incident that I don’t remember being involved in happened when the new one piece plug was delivered and assembled on the cord. After hundreds, maybe thousands of cords were produced with the new plugs it was discovered in the field that they wouldn’t fit into the phones. The plug design was too large for the opening. The Trimline department shut down for two days and with its three shifts cut off the completed plugs on every cord. They re-plugged the cords with a newly designed one piece plug.
The Modular Cord
The modular cord started out as a replacement cord for the Trimline cord but it soon branched out to become the mainstay cord for all types of telephones, computers and other electronic equipment as well.
The modular cord had two variations, starting with a two piece plug that was sonic welded or heat sealed. The clip did not have WE on it. Then came the one piece plugs the color of the cord; soon it was changed to clear. Any telephones with dates before March 1974 that have modular cords have been modified and refurbished. An exception might be field test phones sent to certain cities by Bell Labs.
The first modular cords from Western Electric had color conductors, black, red, green, and white. Soon they went to all black and then all silver. The flat cord made color coding unnecessary.
Production Sequence for the H5AA Trimline Cord
After coiling, reversing and washing the cords were sent to the Trimline Department.
1…Strip both ends
2…Add grommets to both ends
3…Cut string and pick paper
4…Add tips to both ends
5…Bottom clear plastic shells were added to both ends
6&7…Top shells were added and riveted, different operator for each end (now it’s a plug)
8…Inspected and tested 100%
Last Production Sequence Before Modular Cord
1…Strip both ends
2…Add one piece shell and tie a knot in the conductors
3…Add tips
4…Insert tips in slots on shell (now it’s a plug)
5…Inspect and test
H5AA cost cuts were:
                elimination of the string and paper                                                                       
                elimination of gold content
                elimination of two different grommets
                elimination of the different shell
                pieces for one
                elimination of the rivets (5 per
                spring cord)
The first gold tips had a high karat content of gold and locked in a safe when not used-like during the weekend. They are worth their weight in gold.
Cost cuts for gold tips went from high content gold to gold plated then to base metal.
Care of the Cords
The original Trimline cords began like the other cords. When it reached the coiling department—nicknamed boys town for an obvious reason—it joined the other coded cords to be coiled, then heated, then cooled. This put the spring in the cords. Here’s an important piece of information for the collector who may want to get the spring and shape back into their cords. Do NOT boil them in a pan of water! One reason is that the plugs are not to get wet, corrosion and deterioration of the contacts. The second and third is the treatment doesn’t last very long and could cause color fading. Instead put them on a 3/8 inch wood dowel (metal or fiber glass if you have it) and tighten the cord then put twist ties at both ends to hold it in place. Bake it in the oven at 105 degrees. Leave for 10 to 15 minutes, times might vary. Make sure the wood doesn’t catch on fire. After baking, put them in the refrigerator—not freezer—for 10 to 15 minutes. Your cords should be like new for a good while. (All of the Western Electric cords have gone through this process at the factory once, so it shouldn’t take as long. The aged plastic plugs of the Trimline cords were never subject to the heat and cold. It would be good to experiment and start at a lower temp and shorter time. The extreme temperatures might crack the older plastic plugs, therefore don’t go over the recommended temps and times.)  For the non-Trimline cords (spade ends) the temps and times can be increased to 120 degrees and baked for 20 minutes. Refrigeration time can be increased to 20 minutes also.
Mangled, twisted, tangled and backward describe Trimline and other types of Western Electric spring cords that have been abused. Although the main focus of this article is the manufacture and evolution of the Trimline cord, the abuse of all spring cords needs to be addressed. The sight of an abused cord not only looks ugly but its function could be weakened and compromised.
First off all WE spring cords made in the US have the coils lean to the right when relaxed. The coils are tight and firm. If any WE cord leans to the left and are loose they need to be re-twisted (reversed) back into shape.


Don’t have your phone looking good and the cord looks like nine miles of bad road. For modular cords there are detangle adapters for sale.
From my observations most people don’t notice that the cords are an important part of the natural look of the telephone. Also a clean cord enhances the overall appearance of the telephone. A plastic cord cleaner suggested to me, “Arrow-Magnolia”, works well. I haven’t tried it yet. Soap, water and elbow grease works too. The spade tips may get wet but not the Trimline plugs or the modular plugs for the above reasons.
The Trimline Cord as a new innovation played a part in the versatility of the telephone. As stated before it made possible the modular cord which replaced all of the different cords in use including the Trimline cord. I am thankful to have had the opportunity to have been at the start of the residential and business telephone plug era. The last corded phones before cordless.
H5AA and H4DB cord Types

Cord Type #1—Two piece clear plastic riveted shells; grommets, one tapered (angled), one square, both the color of the cord; gold tips; stamped code, length, the quarter and year on metal clips.


Cord Type #2—Two piece clear plastic riveted shells; grommets, one tapered, one square, both the color of the cord; gold plated tips; stamped code, length, year on metal clips.

Cord Type #3—Two piece clear plastic riveted shells; grommets, one tapered, one square, both the color of the cord; base metal tips; stamped code, length, year on metal clips. (Later no stamping on metal clips)

Cord Type #4—Two piece clear plastic riveted shells; grommets, both tapered (error), both the color of the cord; base metal tips; no stamping on metal clips.

Cord Type #5—Two piece color plastic riveted shells; grommets?; base metal tips; stamped metal clips. *
Cord Type #6—Two piece plastic sonic welded shells; one colored tapered, one clear square; base metal long blades; plastic clips, no ID molding on clips; flat cord-Modular type. **
Cord Type #7—One piece tapered color plastic shell, clip and grommet; one piece square clear plastic shell, clip and grommet; base metal tips; no stamping on clips.
Cord Type #8—One piece tapered clear plastic shell, clip and grommet; one piece square clear plastic shell, clip and grommet; base metal tips; no stamping on clips.

Cord Type #9—One piece tapered clear plastic shell, clip and grommet; one piece square clear plastic shell, clip and grommet; base metal tips; no stamping on clips; silver conductors, metal clamp; flat cord.

Cord Type #10-One piece small color plastic plug same on both ends; small copper blades; WE molded on plastic clips; Modular cord, code changed to H4DU.
Cord Type #11—One piece small clear plastic plug same on both ends; small copper blades; WE molded on plastic clips; a) color conductors, b) black conductors, c) silver conductors; Modular cord, code changed to H4DU.
* This cord might have been experimental, not sure if it was manufactured.
** Production of this cord was discontinued in a short time as it led to the small plug Modular cord.
Lengths for Trimline cord H5AA & H4DB – 5’6”, 9’, 13’, 25’?
Lengths for Trimline cord H5AD – 5’6” only (equipped with Message Waiting Lamp)
Lengths for modular cords H4DU – short & standard, long, extra long
Lengths for Trimline cord D5AL – 5’6”, 9’, 13’
Lengths for Trimline cord D5AN - 5’6”, 9’, 13’ (retractable)
H5AA color conductors ran left to right- yellow, green, red, black, white
H4DB color conductors ran left to right- green, red, black, white
H4DU - no color conductors
Beveled (Tapered) Trimline plug fits in the handset.
Square Trimline plugs fits in the base. (spring and straight)
Official BSP Trimline cord colors as of January, 1973
Color         Suffix
Black           03
Ivory           50
Green           51
Red             53
Yellow          56
White           58
Rose Pink       59
Lt. Beige       60
Lt. Gray        61
Aqua Blue       62
Turquoise       64
I’d like to hear from anyone who has other information, corrections or stories about the Trimline Cord.
Richard Gerber, former Western Electric, AT&T Technologies, Lucent Technologies, and Celestica employee. Retired Lucent; ACTA #4231
© 2006