HP / Agilent 4957A Protocol Analyzer

The HP/Agilent 4957A Protocol Analyzer is a portable field instrument for monitoring, decoding, and simulating data communication protocols across serial data networks. It performs multi-layer analysis from physical layer (Level 1) through data link (Level 2) and packet (Level 3), supporting both packet-oriented protocols (SDLC, HDLC, BiSync) and character-oriented protocols (ASCII, Baudot, IBM EBCDIC). The analyzer handles asynchronous and synchronous transmission modes with data rates up to 64 Kb/s in standard configuration and 256 Kb/s with Option 001, extending to 1.544 Mb/s with the HP 18282A ISDN/T1 interface pod.

Technical Specifications Protocol Support

Packet-oriented: SDLC, HDLC, BiSync

Character-oriented: ASCII, Baudot, IBM EBCDIC

Asynchronous and synchronous modes

RS-232C (V.24), RS-449, V.35, X.25

X.21, ISDN BRI/PRI, and T1 via external pods Data Rates and Capacity

Monitoring, simulation, and BERT: up to 64 Kb/s

High-speed monitoring with Option 001: up to 256 Kb/s at 115.2 kbaud

T1 decoding: 1.544 Mb/s with HP 18282A pod

Capture buffer: up to 3/4 MB Measurement and Control

63 programmable triggers for characters, errors, timeouts, and interface transitions

Five timers with 1 msec resolution, maximum 65535 msec each

Five counters, maximum count 65535

Cursor timing: 6 to 66 seconds (rate-dependent) Character Framing and Error Detection

Information bits: 5, 6, 7, or 8 plus parity

Stop bits: 1, 1.5, or 2 (asynchronous)

Error checking: CRC-CCITT, CRC-CCITT preset 0, CRC-16, CRC-12, CRC-6, LRC, parity

Parity modes: odd, even, none, ignore Transmission Control

Send strings: up to 251 characters per string, 1743 characters total

Key Features

High-resolution 13 cm (5-inch) display with VT100 terminal emulation (80-column)

Softkey-driven interface with full ASCII keyboard and cursor control

Five onboard microprocessors

128 KB nonvolatile RAM and 613 KB floppy drive

Integrated patch panel for flexible line connections

Multiple display formats: DTE/DCE overlay, lead status, frame decode, partial packet decode

Bit error rate testing capability up to 64 Kb/s

Typical Applications

Field troubleshooting and maintenance of serial data networks

Protocol compliance and interoperability testing

Network simulation and emulation

Transmission quality assessment via BERT

Compatibility & Integration The 4957A accepts external interface pods designed for HP 4951C and HP 4952A analyzers, enabling expansion to ISDN, T1, X.21, and MIL-188C protocols. Weight approximately 13 pounds.