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The model 102 telephone was Western Electric's first widely distributed telephone set to feature the transmitter and receiver in a common handset. It was produced starting approximately in 1927. Earlier telephones by Western Electric had been of the candlestick type which featured a transmitter fixed to the base, and a receiver held by the user to the ear. Initially the 102 featured a circular base, the A1 mount, a design inherited from the candlestick desk stands, as well as in the redesigned B1 base, produced between 1927 and 1930. Later models, starting in 1930, used an oval design (D1 base) to improve physical stability when dialing. The model 102 telephone consisted of the desktop set (handset mounting) and a physically separate subscriber set (''subset''), a box that was typically mounted on a wall near the phone or on the side of a desk. The desktop unit contained only the dial, a handset cradle with hook-switch, and the handset positioned in the cradle, while the subscriber set contained the ringer and the electrical components to interface the unit with the telephone network. The model 102 was plagued by problems with excessive sidetone feedback into the receiver from the transmitter, resulting in a poor experience for users hearing their own voice very loudly, and in extreme cases in the early handset versions also unstable amplification feedback (howling sounds) from the receiver into the transmitter. The excessive sidetone resulted in users lowering their voice volume to unacceptable levels, causing insufficient audio signal to be transmitted. The model 102 was upgraded in approximately 1930 to the model 202 telephone with better electronic circuitry to solve the sidetone problems. ==History== As early as 1890, Western Electric had been experimenting with handset types that combined the transmitter and the receiver in the same hand-held unit, but two technical problems prevented them from reaching production at that time. First, the transmitters of the day did not work well unless oriented in a vertical plane. If operated at other angles, as would be expected in a hand-held unit, carbon granules in the transmitter would shift and move in an unacceptable manner, resulting in poor voice quality, referred to as carbon noise. Another hurdle to the acceptance of a common handset model was that audio from the receiver was picked up acoustically by the transmitter and amplified, resulting in howling tones, called acoustic feedback, due to the hollow handles providing an acoustic channel between receiver and transmitter. The problems were aggravated by the signal boosting circuitry used in the subscriber set which resulted in a strong signal (sidetone) at the receiver of the speech of the user. Sidetone is desirable only to some fraction of volume so that the user has the assurance that the telephone is working correctly. Strong sidetone may cause users to lower the voice to unacceptable levels, so that the recipient receives insufficient signal level. In the 1920s, developments in anti-sidetone circuitry and non-positional transmitters, which worked in any orientation, permitted Western Electric to develop a handset model free of these problems. The resulting E1 handset was ready for production in 1927. This handset was paired with a base that was essentially a candlestick with a shortened neck of approximately one inch in height, topped with a new cradle for the handset. The cradle incorporated the hookswitch as a vertical plunger actuating the electrical switch contacts. This initial design was tested in the central offices and released in limited supply as Western Electric's first handset subscriber telephone, the model A1. Although the E1 handset was built to complement the anti-sidetone circuitry, such circuitry was still not ready by the time the A-type desk set was released. However, the solid Bakelite construction of the handset suppressed acoustic feedback to acceptable levels. As work continued on the anti-sidetone circuitry, a new base was designed for the E1 handset to replace the shortened candlestick. The new mount was designated by the part number ''B1'', and was similar in overall shape to the A-base, but with more flowing lines and a shell cast completely in aluminum or metal alloy. This is the combination that is most commonly associated with the designation ''102''. During the model's production life, however, it was just referred to by its component parts. The B-type desk set was followed by a wall-mounted handset telephone, designated as the C-type hangup telephone, with the E1 handset hanging on one side of the unit in a cradle for the receiver end. In use, the B-type telephone base proved unstable during dialing, and was replaced with the D-type handset mounting in 1930. A wider, oval base improved its stability. While the D1 mounting base was initially deployed electrically identical to the prior models, advances in the anti-sidetone audio circuitry soon reached production quality, so that D1 sets are most commonly identified as the 202-type telephone. The assembly codes 102 and 202 referred whence to the electrical capabilities of the sets, the 102 having no sidetone reduction, and the 202 containing the anti-sidetone improvements. Thus, some of the early oval D mounts, would still be designated as model 102 if they did not yet have the anti-sidetone circuitry. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Model 102 telephone」の詳細全文を読む スポンサード リンク
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