Diagnostics: Loss of Sync ProLink 6, Port A or B event on PLR

Potential Symptoms

  • Potential poor image quality. A single loss of sync it not likely to cause visual problems for a display, but if multiple losses of sync occur in a ProLink6 circuit, all modules associated with the nodes between the points of failure may go blank.

IDM / System Health Event(s)

  • Loss Of Sync ProLink 6 diagnostics alert (port A or B) on PLR.


  • Product Family:  Billboards, Message Displays
  • Product:  System Health, IDM
  • Component:  PLR, DB-4000, DB-4200, DB-5000, DB-6000, DB-6400, GS6, GT6, GalaxyPro
  • Control System:  
The PLR receives ProLink6 data on two ports - A and B. A loss of sync on one port will cause the PLR to switch to the other port. While a loss of sync itself is a non-visual event, it may be caused by the reset or failure of a ProLink6 node (PLR or VIP-4060) directly connected to the PLR, and therefore may be an indirect indicator of a visual outage.

A persistent loss of sync on a ProLink6 circuit indicates that data redundancy has been lost. Another loss of sync on the same circuit will result in a visual outage affecting all nodes between the two points of failure.


  • This event is created if the ProLink Router (PLR) detects that it is not receiving a ProLink6 signal on Port A or B, causing it to increment a counter.


  1. Look for events indicating that the ProLink6 node connected to Port A or B of the PLR experienced a reset or diagnostic failure, and use the display's webcam to determine if there are any visual issues occurring on the display.
  2. If no such events exist, inspect the fiber optic cable connection between the PLR and the ProLink6 node connected to ports of the PLR.
  3. Reseat or replace fiber between PLR and next device in the signal chain (PLR or VIP).

Related Resources

KB ID: DD4304705

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