Null Modem Cable Serial Crossover D-Sub 2.77-Pitch DB25 25-Pin Male to Male Unbranded Molded Connector 6FT SKU 092717 CB-DB25M-DB25M-xxx Features: Description: Null Modem Cable Serial Crossover D-Sub 2.77-Pitch DB25 25-Pin Male to Male Unbranded Molded Connector 6FT SKU 092717 Manufacturer: Not Specified Brand Name or Distributor: Unbranded Model: (Equivalent & Compatible) Seller's SKU 092717 Connector: D-Sub DB25 2.77mm Pitch 25-Pin Male Molded Connector D-Sub DB25 2.77mm Pitch 25-Pin Male Molded Connector Pinout: (Wiring Circuits checked with an Ohm Meter, not a Spec, for reference only.) A Full Handshaking Null Modem Cable DB25M 1 - DB25M 1 DB25M 2 - DB25M 3 DB25M 3 - DB25M 2 DB25M 4 - DB25M 5 DB25M 5 - DB25M 4 DB25M 6 - DB25M 20 DB25M 7 - DB25M 7 DB25M 8 - DB25M 20 DB25M 9 - NC DB25M 10 - NC DB25M 11 - NC DB25M 12 - NC DB25M 13 - NC DB25M 14 - NC DB25M 15 - NC DB25M 16 - NC DB25M 17 - NC DB25M 18 - NC DB25M 19 - NC DB25M 20 - DB25M 6 & 8 DB25M 21 - NC DB25M 22 - NC DB25M 23 - NC DB25M 24 - NC DB25M 25 - NC Shield - Shield Cable Marking: N/A Item Length: Overall : 6FT Wire: 5.6FT Weight: 5.9 oz (estimated shipping weight 10 oz) Condition: (Subject to Availability) SKU ______A - Aged Open Box, not been used, with signs of cosmetic wear. SKU ______N - New SKU ______B - Bulk New, seller repackaged. SKU ______E - Excess Inventory, not been used, may have signs of age. SKU ______P - For parts, New, please check your device's manual to ensure this pinout configuration matches your connectivity needs. SKU ______O - Open Box, unused, may have signs of cosmetic wear. SKU ______R - Refurbished to working condition. SKU ______U - Used, with signs of cosmetic wear. Package: Non-retail packaging, in Unprinted or Reused Box or Plastic Bag. For use with or pulled from: (for reference only) Null modem cables are not universally interchangeable, they vary in how they handle handshaking. Using the wrong type can result in "digital silence" where devices refuse to communicate because they don't receive the expected hardware signals. Crossover Wiring Null Modem Cable Pin 2 (Receive) connects to Pin 3(Transmit), specifically designed to similar devices (DTEs) like two PCs or a PC and a Printer. These cables are typically restricted to short distance often with a maximum reliable length of about 25 to 30 feet. By how the cable handle 'handshaking' which is the process of devices signaling that they are ready to send or receive data. Simple Null Modem: Only the transmit, receive, and ground wires are connected. It relies entirely on software for flow control. Loopback Handshaking: A specific signal wire is jumpered to another pin in the same connector instead of traveling through the cable to the other device. It tricks the software making it believe a connection is ready even without hardware support from the other side. Partial Handshaking: This crosses RTS/CTS control lines while looping others back locally. Full Handshaking: This crosses all relevant control lines RTS/CTS and DTR/DSR to allow full hardware flow control, supporting higher transmission speeds and more robust communication. While largely replaced by Ethernet and USB for consumer data transfer, null modem cables are still used in several professional fields: Administering Headless Devices - Used to access serial consoles on managed switches, rackmount servers, and embedded systems. Industrial Equipment - Commonly found in utilities (electric, oil, gas) for monitoring RTUs and smart sensing devices. Kernel Debugging - Software developers use them to remotely debug operating system kernels (like Windows via WinDbg or Linux via KGDB) with minimal overhead. Retro Computing - Enthusiasts use them for file transfers and multiplayer gaming on legacy systems like the Amiga or older MS-DOS PCs. Serial Number(s) Available or Sold: SN 0112171 New SN 0112172 New SN 0112173 New SN 0112174 New SN 0112175 New SN 0112176 New SN 0112177 New SN 0112178 New SN 0112179 New