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A silent call is a telephone call that is generated by a predictive dialler (or dialler) which does not have an agent immediately available to handle the call. In this instance the call may be terminated by the dialler, and the called party receives a silence ("dead air") or a tone from the telephone company which indicates the call has been dropped. In the U.S., the Federal Trade Commission (FTC) uses the term "abandoned call" instead of silent call in its regulations applying to telemarketing. "Abandoned call" in non-FTC contexts may refer to a caller who decides not to await answer before hanging up. For more information on why the technology makes silent calls, see predictive dialer. ==Other reasons for silent calls== People using telecommunications devices for the deaf (TDDs) and calling public agencies might expect the agency being called to answer with a TTY. The caller waits for "TTY tones" to be generated over the phone line. The answerer should place the phone receiver into the TTY coupler and type anything ("Hello, Go Ahead") so the caller knows it is connected. For public agencies that have a TTY, it is inappropriate to hang up on a silent call. Many silent calls are a result of process known as pinging. This is very similar to an Internet Protocol (IP) ping, where the intention is to see if there is life at the destination. This is often used by data cleaning companies as a method of removing dead telephone numbers from old lists. Each number is dialed and immediately dropped if the call is connected. If the call is not dropped quickly enough it may result in a short ringing signal. 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「Silent call」の詳細全文を読む スポンサード リンク
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