Digital H3104 DEC Harmonica 8-Port RS-423 Breakout Box DS200 CBL KIT ED932B02

Digital H3104 DEC Harmonica 8-Port RS-423 Breakout Box DS200 CBL KIT ED932B02

The Digital H3104, known as the DEC Harmonica, is an 8-port RS-423 fan-out breakout box designed for use with Digital Equipment Corporation serial systems. It accepts a single 36-pin Champ (Centronics-style) input connector and breaks it out into eight individual RJ modular output jacks, each mapped to one of eight DEC 423 serial ports. The label references connections J1 through J9 covering ports 1–8, with J1 carrying the main 36-pin input (pins 1–36) and J2–J9 providing the individual port outputs.

Specifications & What's Included

• Model: Digital H3104 (DEC Harmonica)
• Part / Serial: ED932B02
• Reference part number: 36-25280-01-C01
• Number of output ports: 8
• Interface standard: RS-423 / DEC 423
• Input connector: 36-pin Champ (Centronics-style) with wire-bail locking clips
• Output connectors: 8× RJ modular jacks (J2–J9)
• Port mapping label: printed wiring diagram on top of unit (ports 1–8, J1–J9)
• Certifications: UL Listed Accessory for use with DEC 423 outputs
• Country of manufacture: USA
• Form factor: compact external breakout box
• Included: breakout box only — no host cable

Applications

The DEC Harmonica family of breakout adapters was developed by Digital Equipment Corporation to simplify the cabling of multi-port serial terminal servers and workstation-attached serial expanders. The H3104 in particular was used with DEC systems such as the DS200 series and compatible VAX/VMS environments, where a single high-density connector on a host card or terminal server needed to fan out to individual RS-423 serial lines for VT-series terminals, printers, and other serial peripherals. RS-423 (EIA-423) is a single-ended asynchronous serial standard that DEC adopted as an alternative to RS-232, offering slightly higher drive capability and longer cable runs. These breakout boxes were standard infrastructure in DEC-based office and engineering environments from the mid-1980s through the mid-1990s, and they remain useful today in any legacy DEC installation that still operates VAX, VMS, or DECserver-based serial terminal networks.