Rewiring A 66 Block From NetGuardian 832A Operation To Work With A NetGuardian 864A

Techno Knowledge Paper: Wiring a 66 Block.

This guide will help you if you are:

  • You're swapping out an 832A for an 864A and you need to rewire alarms.
  • You're wiring a 66 block for a NetGuardian 864A.
Quick Reference Chart.
832a to 854a Wiring

The differences between 832A and 864A wiring.

The 832A features single RTN pins for each point; each alarm consumed 2 pins on the amphenol, one for the alarm, 1 for the return/ground (RTN) path. To increase the discrete alarm capacity for the 864A, alarms each use only 1 pin on the amphenol and are tied to a single, common return pin. Pins 1-24 and 25-32, which were the RTN pins for alarms 1-24 and 25-32 on the 832A will become even numbered alarms, 2-64 on your 864A model NetGuardian.

When rewiring 66 blocks for use with an 864A, you will use a single row per alarm, rather than 2, with all points tied to a common ground (See Figures A and B below to alarming differences between the 832A and 864A). If using a Spit 66 block, you will tie all points to the ground on row A25. If using a straight 66 block, you will tie your alarm points to the common ground on extra, separate 66 blocks.

832a to 854a Figure A
Figure A: A single point on the NetGuardian 832A consumes 2 pins on the amphenol and a pair of 66 block rows.
832a to 854a Figure B
Figure B: Each alarm on the 864 takes up only 1 pin on the amphenol and half a 66 block pair, tied to GND on row A25.

Note: DPS Telecom recommends terminating alarms for NetGuardian 864A units with split-66 blocks.

Things to consider.

Are you using Straight or Split 66 blocks?

If terminating alarms with split 66 blocks, you will need 2 66 blocks, 1 for each amphenol. A split 66 block means that the left two terminals on each row are electrically isolated (split) from the two right terminals.

If terminating alarms with straight 66 blocks, you will need 4 total 66 blocks, 2 for each amphenol.

832a to 854a Figure C
Figure C: A 50-pin split 66 block with rows labeled A1 - S25.

For Split Block Termination:

  1. Remove bridging clips on alarm rows.
  2. Remove clips on rows A1-S24 on the 66-block joined to the first amphenol.
  3. Remove clips on rows A1-S8 on the 66-block joined to the second amphenol.
  4. See figure C on the previous page for example of a split block without bridging clips and rows labeled.
  5. Connect the alarm return path to row A25 on your 66 block.
  6. Bridge the center terminals on row A25 of your 66 block.
  7. Row A25 now constitutes a common return path for your discrete alarms. See figure D below for an example.
832a to 854a Figure D
Figure D: Ground termination on a split 66 block for the NetGuardian 864A.
  1. Wire row A25 to the left terminal for discrete alarm rows.
  2. On the 66 block tied to the first amphenol, wire the RTN path to rows A1-S24.
  3. On the 66 block tied to the second amphenol, wire the RTN path to rows A1-S8.
  4. Re-wire your alarms.

Your 864A 66 blocks should be wired as follows:

832a to 854a Figure E
Figure E: 66 block diagram for discretes 1-48 on the NetGuardian 864A.
832a to 854a Figure F
Figure F: block diagram for discretes 49-64 on the NetGuardian 864A.

For Straight Block Termination:

Note: Because rows on a straight block are not electrically separate, you cannot terminate both the return path and alarm on the same row of a straight block. For straight block termination to an 864A model, you will need 4 total 66 blocks, 2 for alarms and 2 extra 66 blocks to denote the return/ground path. See Figure G at the end of this documentation for an example of straight 66 block wiring.

  1. Disconnect the return path for all alarms.
  2. You will reconnect the return path to your gear on another 66 block.
  3. Connect 2 new 66 blocks to the return/ground path.
  4. Connect a single row to the return/ground path.
  5. Bus rows A1-A25 together.
  6. You will not connect these 66 blocks directly to the 864A unit.
  7. Connect your Return path 66 blocks to your Alarm 66 blocks.
  8. Connect rows A25 on the ground 66 blocks to row A25 on your 66 blocks terminating alarms. See Figure G for an example.
  9. Reorganize alarms on your original two 66 blocks.
  10. Rewire your alarms 1-24 to rows 1-24 (A1-S12) on the first block and rows 1-8 (A1-S4) on the second block. Re-wire each row accordingly and in order. (The diagrams above, discounting the RTN bus, show the order of alarms, 1-48 and 49-64). Note that each alarm will move up a number of rows equal to the alarm number - 1.
832a to 854a Figure G
Figure G: Straight 66-block diagram for wiring alarms on a NetGuardian 864A.

What if I still have a unsolved problem?

If you continue having trouble, please contact DPS Telecom tech support at 559-454-1600 or

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