This is the relationship between the indicator panel cable slots in the backplane for the RP11, and the sections of the indicator panel display for that controller: A32-1 Top left A32-2 Second left B32-1 Third left B32-2 Bottom left C32-1 Top right C32-2 Second right D32-1 Third right D32-2 Bottom right Here is the actual light pattern (unused lights are marked with '-'): XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -XXXXXXXXXXX-XXXX-XXXXXX-XXXXXXXX-X- --XXXXXXXXXXXXXXX----XXXXXXXXXXXXXX- XXXXXXXXXXXXXXXXX---XXXXXXXXXXXXXXX- Note that some (early?) versions are missing ORDY and IRDY, and therefore have this pattern: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -XXXXXXXXXXX-XXXX-XXXXXX-XXXX--XX-X- --XXXXXXXXXXXXXXX----XXXXXXXXXXXXXX- XXXXXXXXXXXXXXXXX---XXXXXXXXXXXXXXX- Here are the detailed contents of the left four rows of lights (top to bottom), and then the right four rows. Signal names are from the RP11 prints; meaning [TBA] is from the RP11 writeup in the Peripherals handbook (if un-marked), from the prints (if marked '[]'; '{}' marks additional explanator material added to make things clear). Caption [some TBA] (where it differs from the signal name) is taken from the drawing of the indicator panel in the RP11 manual (DEC-11-xxxx). Captions of the form 'XXX-N' are intended to have the label above the bar, and the digits below. Signal Caption Meaning SR35 BUFFER REGISTER SR34 SR33 SR32 SR31 SR30 SR29 SR28 SR27 SR26 SR25 SR24 SR23 SR22 SR21 SR20 SR19 SR18 - READ READ WRITE WRIT ERASE ERAS HEAD ADVANCE HA RESORE RS SET CYL SC RESET HEAD RH SET HEAD SH SEEK START SS BOC1 BOC-01 Bus Out Control BOC0 BOC-00 - SCK3 SCK-03 Serial Checksum SCK2 SCK-02 SCK1 SCK-01 SCK0 SCK-00 - - - ERROR ERR HARD ERROR HE ATTN ENABLE AE MODE HEADER HDR DRIVE SEL 2 DRIVE SEL-02 DRIVE SEL 1 DRIVE SEL-01 DRIVE SEL 0 DRIVE SEL-00 NOT READY NR IDE MEX 0 MEX-00 Memory Extension MEX 1 MEX-00 CON 2 COMMAND-02 CON 1 COMMAND-01 CON 0 COMMAND-00 - CAR 7 CYLINDER ADDRESS REGISTER- CAR 6 CAR 5 CAR 4 CAR 3 CAR 2 CAR 1 CAR 0 TAR 4 TRACK ADDRESS REG- TAR 3 TAR 2 TAR 1 TAR 0 SAR 3 SECTOR ADDR REG- SAR 2 SAR 1 SAR 0 - SR17 BUFFER REGISTER SR16 SR15 SR14 SR13 SR12 SR11 SR10 SR09 SR08 SR07 SR06 SR05 SR04 SR03 SR02 SR01 SR00 HEADER WINDOW HW SW 30 HS Header Sync HEADER FOUND HF DATA WINDOW DW SW 34 DS Data Sync SUSP EOS End of Sector - RPMASTER RPM REQ 2 REQ-02 REQ 1 REQ-01 REQ 0 REQ-00 ?? ORDY Silo Output Ready (Note: missing in some versions) ?? IRDY Silo Input Ready (Note: missing in some versions) WCOF Word Count Overflow BAOF Bus Address Overflow - INT REQ INTR Interrupt Request - - - SURDY SRDY Selected Unit Ready HNF Header Not Found SUSI Selected Unit Seek Incomplete SUSU Selected Unit Seek Underdway SUFU Selected Unit File Unsafe UNIT WRITE PROTECTED UWP ATTN 7 UNIT ATTENTION- ATTN 6 ATTN 5 ATTN 4 ATTN 3 ATTN 2 ATTN 1 ATTN 0 - - - WPV Write Protect Violation FUV File Unsafe Violation NXC Non-Existent Cylinder NXT Non-Existent Track NXS Non-Existent Sector PROGE PROG Program Error FMTE Format Error MDE Mode Error LPE Longitudinal Parity Errorx WPE Word Parity Error CSME Checksum Error TIMEE TIME Timing Errorxs WCE Write Check Error NXM NXME Non-Existent Memory Error EOP End of Pack -