How do plans differ?

Starter is free with Calendar, 1 operative, 2 tasks, 1 GB Disk, and Pulse at 30 requests/hour. Signal adds Mail, Channels, Contacts, 4 operatives, 80 tasks, 15 GB Disk, and all three models. Station raises capacity to 20 operatives, 400 tasks, 10 channels, 300 GB Disk, and higher hourly limits. Enterprise is custom for organizations that need tailored deployment and support.