How does the ALCMS communicate?
Commands pass from the control positions through duplicated servers and networks to the field controllers and CCRs, and status and alarms return along the same path.
The ALCMS is built in layers. Control positions, such as the tower and the maintenance station, talk to the ALCMS servers. The servers talk over a communication network to field controllers in the substations, and these connect to the CCRs that power the series circuits. A command such as a new brightness step travels down through the layers, and circuit status and alarms travel back up the same way.
Because pilots depend on the lights, the important links are normally duplicated: two servers and separate network paths, so one failure does not remove control. The design still assumes something can fail, so each CCR keeps a local control option at the CCR or substation. The number of layers, the connection types and the redundancy vary with the manufacturer and the project, so the project design documents are the reference for any actual site.
Frequently Asked Questions
Q1What does the ALCMS communication architecture describe?
It describes how control commands and monitoring data travel between the operator positions, the ALCMS servers, the communication network, the field controllers in the substations and the CCRs that supply the series circuits.
Q2Why are the servers and networks usually duplicated?
The ALCMS controls lighting that pilots rely on, so one failed server, switch or cable should not remove control. Duplicated servers and separate network paths let the system carry on after a single failure. How much redundancy is provided depends on the project design.
Q3How does a command reach a CCR?
The operator selects a command, such as a brightness step, at a control position. The server passes it over the network to the field controller in the substation, and the field controller passes it to the CCR through a hardwired, serial or network connection. The CCR then changes its output.
Q4Is monitoring a separate system from control?
It uses the same path in the opposite direction. CCR status, circuit status and alarms travel back through the field controller, network and server to the operator. A correct display should show the status fed back from the equipment, not just the command that was sent.
Q5What happens if the network or a server fails?
The CCRs normally stay in their last commanded state and can be switched to local control at the CCR or substation, but the exact behaviour depends on the design. Remote control and monitoring are lost for the affected part until communication is restored, and ATC is told as the airport procedure requires.
Q6Who may change the network or ALCMS settings?
Only authorised engineers, under the airport's change control and after testing. Addresses, settings and software on a live system are not altered casually, and the control network is kept separate from general airport IT networks as the design requires.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.