HP 40290-60007 - Loopback connector - For 50-pin RS-232C connector - For testing all ports on the RS-232C ATP 37/M PC board Retail
HP 40290-69042 - RS-422 advanced terminal processor (ATP 37/M) board - Has 50 pin connector on rear (for attaching cable to external connector panel) - RS-422 Advanced Terminal Processor (ATP 37/M) Board (Option 105) - Has 50 Pin Connector on Rear (f Retail
HP 40290-69041 - RS-232C advanced terminal processor (ATP 37/M) board - Has 50-pin connector on rear - RS-232C Advanced Terminal Processor (ATP 37/M) Board (Standard) - Has 50 Pin Connector on Rear (for Attaching Cable to External Connector Panel) Retail