HP 18177A V.35 DTE/DCE Interface Panel for HP 4951C Protocol Analyzer

HP 18177A V.35 DTE/DCE Interface Panel for HP 4951C Protocol Analyzer

The HP 18177A is a V.35 DTE/DCE interface panel designed specifically for use with the Hewlett-Packard 4951C Protocol Analyzer. This pod-style interface module connects between the HP 4951C and a V.35 serial link, allowing the analyzer to monitor and decode both DTE and DCE signal states in real time. Front-panel LED indicators display MARK/SPACE status for all key V.35 circuit lines simultaneously, giving technicians an at-a-glance view of signal activity on the interface under test.

Specifications & What's Included

• Model: HP / Hewlett-Packard 18177A
• Interface standard: V.35
• Interface mode: DTE and DCE monitoring
• DTE signal LEDs (MARK/SPACE): DTE (Transmit Data, CCITT 103), SCE (Serial Clock Transmit External, CCITT 113), RS (Request to Send, CCITT 105), DTR (Data Terminal Ready, CCITT 108/2)
• DCE signal LEDs (MARK/SPACE): DCE (Receive Data, CCITT 104), SCT (Serial Clock Transmit, CCITT 114), SCR (Serial Clock Receive, CCITT 115), CS (Clear to Send, CCITT 106), DSR (Data Set Ready, CCITT 107), CD (Carrier Detect, CCITT 109)
• Connectors: dual 34-pin Winchester V.35 connectors (pod cable connectors for HP 4951C)
• CCITT circuit reference table printed on front panel
• Compatible with: HP 4951C Protocol Analyzer
• Form factor: external interface pod/panel module
• What's included: HP 18177A interface panel only — no pod cables included

Applications

The HP 4951C Protocol Analyzer was a widely used serial data communications test instrument from Hewlett-Packard, designed for testing and troubleshooting synchronous and asynchronous serial links in telecom, data networking, and industrial communications environments. Interface panels like the 18177A served as interchangeable pods that adapted the analyzer to specific physical and electrical interface standards — in this case V.35, the ITU/CCITT standard for high-speed synchronous serial communication commonly used on leased-line WAN links, CSU/DSU connections, and router-to-DSU cabling in the 1980s and 1990s. By inserting the 18177A between the DTE (router, bridge, or terminal) and the DCE (modem or DSU), technicians could monitor all V.35 circuit states in real time, capture data, and diagnose protocol and handshaking problems without breaking the circuit. This type of passive monitoring pod was a standard tool in telecom labs, carrier field engineering kits, and data center operations teams maintaining Frame Relay, X.25, and leased-line WAN infrastructure. The 18177A is the correct replacement or spare pod for anyone maintaining an HP 4951C analyzer that handles V.35 circuits.