| 摘要 |
<p>In an interface device for interfacing a telephone instrument, such as a headset, a handset, a modem, or a teleconferencing device, to the handset microphone input port of a telephone set base unit, the transmit signal level applied to the microphone input of the base unit must be set to an appropriate level. The appropriate level is determined according to the type of microphone the telephone set base unit is configured to interface with. The microphone can be carbon, electret or dynamic. The interface device detects the type of microphone the base unit is configured to interface with by detecting the DC characteristics of the microphone input port. Then, the interface device determines the appropriate transmit level by correlating the DC characteristics to one of a plurality of predetermined transmit levels. These levels are stored in a table. The transmit signal level is then automatically set according to a selected one of the predetermined transmit levels. Alternately, a test signal is applied to the microphone port of the base unit to determine its input characteristics and, then, the transmit sensitivity is set based upon this determination. A test signal can alternately be applied to the microphone located in the handset to determine its type or characteristics and, then, the transmit sensitivity is set based upon this determination. As an enhancement, receive sensitivity is adjusted for signals received from a handset speaker output port.</p> |
