“Model 202 telephone”的意思、由来-开放百科全书

The model 202 telephone was a desktop telephone produced by Western Electric for the Bell System from 1930 to 1939, and by Northern Electric in Canada. Refurbished units were installed into the mid-1950s. It was an updated version of the 102-type telephone, containing the newly developed anti-sidetone circuitry to reduce electronic feedback from the transmitter (mouthpiece) to the receiver (earpiece).

Like the 102 hand telephone, the 202 telephone consisted of the desk-top telephone instrument with the telephone handset and a physically separate subscriber set (desk set box) which contained the ringer and the electrical components to interface the desk set with the telephone network. Visually, it was indistinguishable from the 102.

History

The 102- and 202-type telephones were developed from previous hand telephone versions based on the A- and B-type handset mountings which featured a circular base. The A handset mounting was a direct derivative of the candlestick telephone with a shortened vertical shaft, but had a handset cradle mounted on the top, instead of a sideways extending switch hook. The B-type handset mounting was a resculpted variety that integrated the vertical shaft into the contours of the still circular base. The circular base proved unstable during dialing, however, and therefore a new, wider, elliptical base was developed and introduced in 1930. This design was referred to as the D handset mounting. This newly designed telephone initially used the same sidetone electric circuit as the predecessors, but soon it was also equipped with the new anti-sidetone circuit that provided much improved audio performance.

While some sidetone is desirable, reassuring the user that the set is operating properly, too much sidetone created an unpleasant experience when the users heard their own voice or ambient sound very loudly. This causing them to lower their own speech volume to low levels unacceptable for transmission. The anti-sidetone circuitry contained a modified transmission hybrid transformer (induction coil) that reduced sidetone to proper levels.

With the introduction of anti-sidetone circuits in subscriber telephones in 1930, Western Electric began assigning assembly codes to telephones based on the electrical configuration. Until then, telephones were primarily referred to by the part designations used to construct them. With the new circuit variants, this became insufficient, resulting in the distinction between 100-series hand telephone sets and 200-series hand telephones. Thus, the type 102 was the new designation for the D1 hand telephone when used on common battery lines with a sidetone circuit,^[1] and the 202 was the anti-sidetone version of the D1 handset mounting.^[2] The previous types, i.e. the A and B handset mounting were not designated with these new codes.^[3]

Construction

The 202 telephone, like the 102, consisted of two distinct parts. The desk-top set, containing only the dial and a cradle that secured a handset, which combined the receiver and the transmitter elements in one unit, in the on-hook position. The cradle contained a plunger that operated the hookswitch located underneath the cradle, inside the housing. The second part was a physically separate subscriber set (desk set box), in form of a metal or Bakelite box, which contained the ringer and the electrical components to interface the desk set with the telephone network. The desk set was connected to the subscriber set with a four-conductor mounting cord. The subscriber set was typically mounted either on the wall in close proximity, or to the rear or underneath a desk.

Newly manufactured units used the E1 type handset, whose development period began in ca. 1921 and was completed by 1927. The handset was molded in Bakelite, but the receiver and transmitter assemblies had an aluminum metal core. Its transmitter assembly that was extended by a hollow mouthpiece, known colloquially as a spit cup, to focus sound more effectively into the transmitter. The barrier-button transmitter element exhibited a cone shape into the spit cup, known as a bullet transmitter among collectors. This feature was eliminated about halfway through the handset production run, when in 1934 the transmitter element was changed to a more efficient type (F1) with better voice reproduction. The F1 element had a flat disk shape and was protected by a simple plastic screen as moisture barrier and a cover grill. This element became the standard transmitter of a new handset type (F) in 1937, and was in use in the Bell System until the 1960s. When this new handset became available, 202-type telephones were often refurbished with the new handset.

The vast majority of the original production run of the 202-type telephones were produced in black finish. For an extra fee, telephones and subscriber sets could be ordered in several other colors, both flat colors or hues with metallic luster.

Evolving models

In the 1950s, large quantities of old telephones were retired in favor of the popular new model 500 telephone, creating a stock pile of still usable parts. In 1955, Western Electric reissued the 202 painted in several colors, in an effort to use up these existing parts stocks, and to satisfy the growing demand for color telephones. The new manufacturing processes to produce the new line of color sets based on the 500-type telephone were not completed yet, and those set were only issued in black until 1953. The Continental line was created from a D1 base with an F1 handset, and was available painted in primarily ivory, green, red, and black, but other colors were made available by special customer order. The Silver Continental was a D1 base, plated in silvery rhodium and coupled with an ivory painted or molded ivory plastic handset. The Imperial was sprayed with gold lacquer, and was also supplied with an ivory painted or molded ivory plastic handset.

History

Construction

Evolving models

See also

References

External links