Америкалық 500 үлгісі телефон аппаратының тарихы

Type of American telephone set

The Western Electric model 500 telephone series was the standard domestic desk telephone set issued by the Bell System in[North America from 1950 through the 1984 Bell System divestiture. The successor to the model 302 telephone, the model 500's modular construction compared to previous types simplified manufacture and repair and facilitated a large number of variants with added features. Touch tone service was introduced to residential customers in 1963 with the model 1500 telephone, which had a push button pad for the ten digits. The model 2500 telephone, introduced in 1968, added the * (asterisk) and # (pound) keys. The model 500 telephone series and its derivatives were very popular and common among North American businesses and households throughout the latter half of the 20th century. The development of new simpler telephone set designs, the advent of mobile phones, and the decline of traditional landlines into the 21st century led to the decline of the model 500 series and its derivatives, and most sets still in use are primarily kept by seniors and phone enthusiasts for familiarity, collecting, and nostalgia. However, the model 2500 is still produced by several manufacturers as of the early 2020s, with modernized components to ensure compatibility with modern Bluetooth and voice over IP telephony systems.

The Western Electric 500 type telephone replaced the 300 type, which had been produced since 1936. The model 500 line was designed by the firm of industrial designer Henry Dreyfuss, the product of several years of research and testing in collaboration with Bell Laboratories and Western Electric. Development started in 1946 with early sketches by Bell engineer and Dreyfuss associate Robert Hose, leading to pre production units in 1948 and field trials with 4000 telephone sets in 1949. AT&T announced the new telephone publicly in 1949 and communicated the first availability of approximately 23,000 sets in the second quarter of 1950 to the Bell System operating companies on May 1, 1950. Third and fourth quarter production was estimated at 49,000 and 93,000, respectively. Including 20,000 units of a special purpose set (501B), approximately 183,000 units were produced by the end of the first production year. In the following years, the systematic replacement of 25 million 300 type telephones commenced because of the new model's much improved electrical and acoustic efficiency. This efficiency permitted the new model to be used on long rural loops, which previously required special sets with local batteries to power the transmitter, not just on urban short loops because it contained a self adjusting gain control. This also permitted the use of thinner loop wires and thus delivered cost savings in the build out of the network. A 1953 Western Electric ad noted that the “500” phone “has already been introduced on a limited scale and will be put in use as opportunity permits, in places where it can serve best.”

The replacement of 300 series telephones with 500 series sets created large stockpiles of 300 type components that had not reached their intended service life. The accelerating demand for new telephone service in the 1950s created pressure on the manufacturing facilities, which the Bell System alleviated by reusing these older components to refurbish used 302 telephone sets with a new modern housing that had a look alike appearance to the 500 models, but were electrically identical to the older 302 telephones. This program commenced in 1955, and the converted set was labeled as the model 5302 telephone. It was produced until the mid 1960s in the refurbishing shops of each Bell Operating Company, not on the assembly lines of Western Electric factories. From the 1949 field trials until 1953, only black sets of the 500 type telephone were manufactured. Telephones in color were introduced in several stages from 1954 until 1957, as manufacturing capability was refined and material selection processes were completed. In the 1960s, after the introduction of touch tone service in November 1963 in various locations of the telephone network, the basic 500 type chassis was retrofitted with a new housing and face plate, and a ten key push button keypad. This was designated as the model 1500 telephone, and a twelve button model 2500 was introduced in 1968. The 1970s brought the conversion to modular connector technology, replacing the hard wired cords with cords terminated on both ends with 4P4C connectors for the handset cord and 6P4C plugs for the line cord.

As with most telephones in the United States, the 500 series telephones were owned by the local Bell Operating Company and leased on a monthly basis to customers. Choices for telephone styles and colors were limited. AT&T, the principal owner of the operating companies and Western Electric, strictly enforced policies against buying and using telephone sets by other manufacturers on their network to ensure the technical integrity of their network and avoid competition. Most phones made by Western Electric, starting in about 1968, carried this disclaimer molded into their housing: "BELL SYSTEM PROPERTY NOT FOR SALE." Telephones were also sometimes labeled with a sticker or ink stamp marking the operating company's name that owned the phone. After consumers started buying telephones from other manufacturers, in the wake of legal developments not favoring AT&T's ban against third party equipment, AT&T changed its policy for the Design Line telephone series by selling customers the telephone housing but retaining ownership of the electrical components, so customers were still required to pay AT&T a monthly leasing fee. In 1983, after the court ordered the Bell System divestiture, AT&T started selling telephone sets outright to the public through its newly created American Bell division. Many customers were offered the option to buy the leased telephones they had in service. AT&T closed its USA consumer telephone manufacturing plants in 1986 and moved production offshore to Singapore, China, and Thailand, and in the 1990s to Mexico; this let them produce telephones at a lower cost.

The Western Electric model 500 improved upon several design features over the earlier telephones. While the 302 had the dial and hook switch mounted directly on the metal or plastic housing, all operational parts of the 500 telephone were mounted on the base plate, and the housing only contained two plungers to activate the hook switch when the handset was lifted from the cradle. Thus, the phone could be tested and serviced easily without the housing. This design improved manufacturing and servicing efficiency. The earlier 302 had been equipped with an enamel coated dial plate that displayed the numerals and letters through the holes of the rotary finger wheel. Years of use caused the lettering and numbering, and even the porcelain coating, to wear off. The design of the 500 improved this by molding the characters into the plastic through a double injection molding process. This design was carried over to the 1500 and 2500 series telephones and was used in the touch tone keys to eliminate wear. The numbers and letters on the 500 were moved to the circumference of the dial plate to make them visible from a wide range of viewing angles even while the dial was spinning back to its resting position. Dots were placed in the center of the finger holes as targets to help position the finger quicker for dialing of the next digit while the wheel was still spinning back. After extensive testing, this arrangement had the benefit of reducing dialing errors and increasing the speed of dialing each digit by fractions of a second. The 500 series replaced many metal parts, especially in the dial, with much more durable Nylon components. The Dreyfuss design later adapted itself well to touch tone service, first announced in 1963. The earliest experimental touch tone phones used the original Dreyfuss design almost unchanged; the keypad, in varying layouts, was placed in a roundel in the dial opening, with the subscriber number label in a small window below. The 1500 and 2500 models adopted a more angular design style; the curves of the original design gave way to raised borders forming a lip around the finely ribbed faceplate, in the middle of which the keypad and number window was centered. Electrically and acoustically, the 500 series telephones had better efficiency and gain characteristics than their predecessors. The transmission efficiency was 5dB higher, and the receiver efficiency was 2.5dB better on long loops than on the 300 series telephones. A significant improvement was the use of equalization circuitry to achieve automatic gain adjustment. The sets could be deployed with equal performance on short or long local loops from the central office. The G type handset was newly developed to help realize this efficiency. The older F series handset was already operating at the peak of its acoustic and electrical design efficiency. The G handset remains the standard handset on many phones, including public payphones. For the initial years, from 1950 to 1953, the 500 was available only in black with a metal finger wheel. In 1954, color telephone sets were available in ivory, green, dark gray, red, brown, beige, yellow, and blue. Gray, blue, yellow, and red sets were initially assembled with black dials until the colored parts became available by 1955. So called two tone color varieties were available, which consisted of a black set having the housing substituted with a color plastic part. Starting in 1963, the Dreyfuss design adapted itself well to the newly announced Touch Tone® service. For the trial period, the dial was replaced with circular closure containing a keypad and a telephone number label. The 1500 and 2500 models adopted a more rectangular design style; the curves of the original design gave way to raised borders forming a lip around the finely ribbed faceplate, in the middle of which the keypad and number window was centered. Standard touch tone telephones generate twelve DTMF signals in a grid of three columns and four rows of buttons. In contrast, some special purpose telephones are equipped with a fourth column of keys for the A, B,C, and D DTMF signals for service priorities in the AUTOVON system. Original sets used a transistor oscillator; newer phones use an integrated circuit. The model 1500 only had push buttons for the ten digits, while the model 2500 used 12 keys and included the '*' and '#' DTMF signals to allow for extra signaling needed in advanced service features, such as voice response systems and call management.

Beginning in the early 1950s, 500 style phones were also made under license by ITT Kellogg (now Cortelco), who continued manufacturing the original rotary design, marketed as the Cortelco ITT 500AS (desk phone) and Cortelco ITT 554AS (wall phone), until discontinuation on January 1, 2007. The design was also produced in Canada by Northern Electric, which eventually became Northern Telecom. Cortelco continues to produce a non dial version of the model 500, known as the Model 89001047PAK; this phone is available only in bright red color. Stromberg Carlson (now part of Siemens) also made the phones from the 1950s 1980s. Some contemporary replicas of the 500 model are available. While faithful from a cosmetic point of view, they are internally very different from the original, including a rotating tone dialer based on optical technology.

The Western Electric model 1500 telephone adapted the 500 design for touch tone dialing with a push button pad for the digits 0 through 9. It was produced from 1963 to 1968. In addition to the basic single line model 1500D, the 1500 series included many related variations and special purpose models with additional features. This included sets with a headset jack, 2 line sets (1510F), key sets (1560), call directors, panel phones (1750), industrial phones (1520), and automatic dialers (1660).

By the late 1960s, interactive response systems in some industries required additional signaling beyond the ten digits. In 1968, the push button dial pad was extended with two additional keys, the * (asterisk) and # (pound), which marked the introduction of the 2500 type telephone. The additional keys were located on either side of the 0 button to fill the matrix of 4 by 3 keys. These keys were initially unused by most customers but would later be used for vertical service codes and voice mail menu navigation. In 1974, when modular connectors were introduced, the 2500 telephone was fitted with modular connectors on handset and line cords, resulting in type designations suffixed with M, e. g., 2500DM. In addition to the basic single line model, the model 2500 series included many related variations and special purpose models with additional features. This included sets with a headset jack, 2 line sets, keysets (2560), call directors, panel phones (2750), industrial phones (2520), automatic dialers (2660). Though less common than it was in its heyday, modernized model 2500 sets are still produced by several companies as of 2024, primarily Cortelco, in numerous variants including basic sets and those with hook flash and message waiting indicator features.

The Model 500 series, and its distinctive ring, are near ubiquitous in late 20th century U. S. and Canadian film and television. Model 500s are featured as a weapon in the movie True Lies.