| 摘要 |
<p>A process transmitter communications circuit (20, 96) has link terminals (40) which are coupled to a process link (12), which supplies power to the circuit. A power source (38) is coupled to one of the link terminals and is independent from the power supplied from the process link (12). Communications circuitry (42) is coupled to the power source (38) and link terminals (40), which transmits a transmitter signal over the process link (12), through the link terminals (40). A power sensing component (44) is coupled to at least one of the link terminals (40) and the communications circuitry (42) and senses whether the power supplied by the process link (12) is inadequate to transmit the transmitter signal. A power control component (46) is coupled to the power source (38), the link terminals (40) and the communications circuitry (42) and selectively applies power from the power source (38) to the communications circuitry (42) for transmitting the transmitter signal when the power sensing component (44) senses there is inadequate power supplied by the process link (12).</p> |
