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Voice Feature Guide 01

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).


This section describes accounting on pay phones using coins or IC cards.


The AG supports three types of accounting: polarity reversal accounting, 12/16KC accounting, and polarity reversal pulse accounting.
  • Polarity reversal accounting: The pay phone starts to account immediately after detecting a voltage reversal between A and B wires.
  • 12/16KC accounting: It is also called KC accounting. The pay phone performs accounting based on 12 kHz or 16 kHz high frequency signals sent by the POTS board.
  • Polarity-reversal pulse accounting: The pay phone performs accounting based on standard pulse signals sent by the POTS board.

Polarity Reversal Accounting

Polarity reversal refers to the voltage reversal between wires. For example, if the voltage between A and B wires is Vtp, the reversed voltage is -Vtp. After detecting a polarity reversal signal, the pay phone starts to account. The pay phone stops accounting when the voltage between A and B wires changes from -Vtp to Vtp, as shown in Figure 1-17. The polarity reversal is classified into hard polarity reversal and soft polarity reversal.
  • Hard polarity reversal: also called quick polarity reversal. Specifically, the voltage is reversed in a short period of time, shorter than 3 ms in general. The hard polarity reversal brings great interference on lines.
  • Soft polarity reversal: also called slow polarity reversal. Specifically, the voltage is reversed in a long period of time, longer than 80 ms in general. The soft polarity reversal brings small interference on lines.
Some terminals are faulty if the polarity reversal time is long. In this situation, the hard polarity reversal must be used, although it brings great interference on lines.
Figure 1-17 Hard and soft polarity reversal

12/16KC Accounting

When detecting that both the calling and called parties enter a session, the softswitch/IMS requests the AG to send 12 kHz or 16 kHz high frequency pulse signals to the pay phone. The pay phone performs the accounting once after detecting such a pulse signal. For example, if the carrier charges subscriber 1 cent for one-minute call, the softswitch/IMS sends such a pulse signal at the interval of one minute. If the pay phone receives three such pulse signals after the call ends, the subscriber is charged 3 cents. After detecting that the call ends, the softswitch/IMS requests the AG to stop sending such pulse signals to the AG.

Polarity Reversal Pulse Accounting

The principle of the polarity reversal pulse accounting is the same as that of the polarity reversal accounting. The difference lies in that the POTS board sends standard pulse signals to pay phones. As shown in Figure 1-18, the pulse width is Tw and there are a total of two pulse signals.
Figure 1-18 Polarity reversal pulse accounting
Updated: 2019-02-22

Document ID: EDOC1100067358

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