M970

This document is a proprietary schematic for the "Cable Interface BD. #1," designed by Digital Equipment Corporation in 1971, intended for test and maintenance purposes.

The primary focus of the schematic is to define the functions of modem jumpers when installed. These functions include:

• Configuring secondary transmit and receive data lines to EIA pins 14 & 16, or pins 11 & 12 (associated with "202" signals).
• Enabling "Ring" and "Data Terminal Ready" functions for Bell 303 series modems ("301").
• Monitoring the Bell 811B restraint function ("811").
• Forcing a "BUSY" function when combined with a request to send. It also notes a specific jumper removal for Bell 301 use.

The document includes a detailed graphical representation of these connections and signals, along with a Parts List specifying components such as a flip-chip handle, split lugs, eyelets, a right-angle header connector, and the etched circuit board itself. The board is identified as part number M970-0-1, Revision C.