Using the wrong type of serial cable can easily lead to connection issues. Serial ports typically connect through 9-pin or 25-pin connectors, and the cable must match the port type on both devices. The optical probe attaches to the optical port on the front of the meter and allows on- site communications (for example, with a laptop computer). Additionally, RS-232 applications generally require either a “null-modem” or “straight-through”. Manuals and User Guides for Keysight N7745A Optical Power Meter. We have 2 Keysight N7745A Optical Power Meter manuals available for free PDF download: User Manual, Getting Started Manual Keysight N7745A Optical Power Meter Pdf User Manuals. Use straight cable to a switch, cross over for a direct meter-to-computer connection Can you Ping the meter? What are the results? IP Address conflicts? (Meter does not support DHCP) Too many users? Try: telnet <meter IP> Check diagnostics viewer from. We declare that the accompanying product, identified with the mark, complies with the requirements of the Electromagnetic Compatibility Directive, 2004/108/EC and the Low Voltage Directive 73/23/EEC. To operate correctly it is essential that both devices.