| 摘要 |
A telephone alerting device for connection to a telephone line and a telephone. When the telephone is off-hook, the device will generate a visual alarm and a periodic audio alarm in the ear-piece of the off-hook telephone if an additional telephone connected to the same line also goes off-hook, thereby providing an eavesdropping alarm. Also provided is a telephone privacy and alerting device for connection between a common telephone line and a telephone device, which includes a privacy circuit to prevent the telephone device from accessing the telephone line when another telephone device is already off-hook, and an alerting circuit to indicate an alarm when the telephone device is off-hook and a further telephone device is also off-hook.
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