A Cisco 26-pin DCE/DTE cable is a specialized serial cable used to connect a Data Communication Equipment (DCE) device to a Data Terminal Equipment (DTE) device, such as connecting a router to another router, a modem, or a CSU/DSU (Channel Service Unit/Data Service Unit) in a Wide Area Network (WAN) environment.
The 26-pin connector is also known as a Smart Serial connector, which is a Cisco proprietary interface. The cable is typically used with Cisco routers and switches for high-speed serial WAN connections. The DCE/DTE designation in the cable's name refers to the roles that the connected devices play in the data communication process:
DCE (Data Communication Equipment) - This is typically a device that provides a clocking signal and is responsible for establishing, maintaining, and terminating the communication link. Examples include modems and CSU/DSUs.
DTE (Data Terminal Equipment) - This is typically an endpoint device that initiates and terminates the data transmission, such as a computer, router, or switch. When connecting two devices, it's essential to use the correct DCE/DTE cable to ensure proper communication between them. The cable will have different pinouts for each end, allowing the devices to communicate effectively.(Source Chat GPT4)