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AN97

更新时间： 2022-11-29 07:39:03

品牌	Logo	应用领域
美信 - MAXIM		电话
页数	文件大小	规格书
5页	463K
描述
Telephone Tone Generator Requires No trimming

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AN97 数据手册

SIGNAL GENERATION CIRCUITS

Application Note 97: Jul 09, 1998

Telephone Tone Generator Requires

No Trimming

Many products that connect to phone lines (modems, for instance) incorporate a "call-

progress monitoring" function known as CPM. CPM circuits "listen" to the lines as a

human would, and respond according to what they "hear." You shouldn't dial a number

unless you first hear a dial tone, for example. Neither should your computer.

Tone accuracy is not very important when people monitor the call-progress tones, but the

use of computers for this purpose has produced a need for tone-accuracy specifications to

prevent errors in interpretation. Accordingly, CCITT has introduced the North American

Precise Audible Tone Plan (the following data is from the CCITT Green Book, Volume

VI-4):

Figure 1 illustrates a simple circuit for generating single or dual tones. They must be

±±.5ꢀ accurate in freꢁuency, and they must be gated as shown in the "Cadence" column

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