The Avaya / Lucent 603H1 is a model of the CallMaster IV Digital Voice Terminal, used primarily in call‑center and operator-console environments. It’s part of the classic CallMaster series designed for Definity / Communication Manager systems.
It appears as 603H1-A or 603H1-A-003 in listings.
It is consistently described as a CallMaster IV Voice Terminal.
Often associated with Avaya part numbers like 700274570, 700275647 or 700275704 (variants or related assemblies).
This identifier corresponds to a specific hardware revision of the Avaya / Lucent CallMaster IV digital voice terminal.
CallMaster IV
Used in call‑center and operator environments
Designed for Definity / Communication Manager systems
Headset‑centric terminal (often no traditional handset)
603H1 → Base model (CallMaster IV)
A → Hardware revision
(77) → Manufacturing or firmware batch code
003 → Sub‑assembly or production variant
These suffixes don’t change the functional identity — they simply indicate the exact build version.