Configuring WinCC Horn Alarms: Single, Redundant, and Client Stations

The SIMATIC WinCC Horn Editor is the dedicated tool for triggering audible alarm signaling on operator stations. In distributed topologies, however, the Horn Editor is frequently the source of recurring field issues: horns that fire only on the engineering server, horns that stay silent on OS clients in a redundant pair, or horns that fail entirely after a server failover. This reference consolidates the configuration procedure for single-user stations, redundant servers, and OS clients, and provides the proven C-script workaround that activates audible alarms on clients when the standard horn assignment fails.

1. Horn Editor Architecture in WinCC / PCS 7

The Horn Editor is a WinCC subsystem that ties acoustic signaling to message-class events. Each instance of WinCC Explorer on a server, redundant server, or OS client runs its own Horn Editor, and the runtime behavior of the audible alarm depends on which instance owns the message class assignment.

Critical architectural constraint: in a multi-station project, the Horn Editor must be opened and configured on every WinCC station that is expected to emit the audible signal. A configuration present only on the master server will not propagate acoustic playback to OS clients or to the standby partner in a redundant pair.

2. Prerequisites

Before configuring the Horn Editor, verify the following:

• WinCC Explorer installed and project opened on the target station (single, server, redundant server, or OS client).
• Audio hardware (sound card, speakers, headset) installed and functional on the OS. Test playback with a standard .wav file in Windows Media Player first.
• Project message classes already defined in the Alarm Logging editor (e.g., "Alarm", "Warning", "Fault").
• For redundant systems: WinCC Redundancy package licensed on both partners and redundant server pair active.
• For OS clients: WinCC Client license installed and OS client project loaded on each client.
• Valid .wav file (PCM, 8/16-bit, 11.025/22.05/44.1 kHz) of small size to avoid latency on message bursts.

3. Horn Editor Configuration Procedure

The standard procedure, derived from the Siemens PCS 7 Horn FAQ, is identical for single-user stations, servers, redundant servers, and OS client stations. The procedure is executed on the local WinCC Explorer of each station.

Step 1 - Open the Horn Editor

1. Start WinCC Explorer on the target station.
2. Double-click the Horn icon in the WinCC Explorer navigation tree.
3. The Horn Editor opens with a worksheet showing message class assignments.

Step 2 - Assign Message Class

1. In the Horn Editor worksheet, click the row corresponding to the desired message class (for example, Alarm).
2. Open the event class pull-down menu and select the Alarm message class. Confirm the message class filter matches the alarms you want to make audible.
3. Repeat for additional message classes (Warning, Fault, System) as required.

Step 3 - Assign WAV Resource

1. For each message class row, click the horn icon in the row to open the resource selection dialog.
2. Browse to the project Horn subfolder (typically <Project>\HmiRun\Horn\ or the path visible in WinCC Explorer under Horn).
3. Select the .wav file to play when a message in this class arrives.
4. Confirm the selection. The file is referenced by path in the Horn Editor.

Step 4 - Activate Runtime

1. Start WinCC Runtime on the configured station.
2. Trigger an alarm of the configured message class to verify playback.
3. If playback fails on a client station, proceed to the C-script workaround in Section 6.

4. Configuration by Station Type

4.1 Single-User Station

The simplest topology. A single WinCC station hosts engineering and runtime. Configure the Horn Editor on this station only. The .wav file must exist in <Project>\HmiRun\Horn\. There is no replication requirement because no other station exists.

4.2 Non-Redundant Server

One WinCC Server with one or more OS Clients. Configure the Horn Editor on:

• The WinCC Server if the server console must sound alarms.
• Each OS Client if the operator positions must sound alarms.

The message class assignments on each client must mirror those on the server. The alarm message itself is delivered to the client via the WinCC server-client data path; the Horn Editor on the client evaluates the message class locally and plays the local .wav.

4.3 Redundant Server Pair

Two WinCC Servers (Master and Standby) with automatic failover. Configure the Horn Editor on:

• Both server partners (Master and Standby) so the audible alarm is preserved after failover.
• Each OS Client attached to the redundant pair.

Failover behavior: When the Master fails, the Standby becomes the active server. OS clients reconnect to the new Master. Because the Horn Editor is configured on both partners and on each client, audible signaling continues without manual intervention.

5. WinCC Version-Specific Behavior

6. C-Script Workaround: Audible Alarms on OS Clients

Symptom: Horn Editor is configured correctly on the WinCC Server and on the OS Clients. Server console sounds the alarm as expected. OS clients receive the alarm message (visible in the Alarm Logging view) but do not produce any audible signal. This failure mode is documented in field reports against WinCC V7.3 in redundant server topologies.

Root cause: The Horn Editor message class binding does not always propagate to the OS client runtime in certain project configurations, particularly when the OS client project was created by project duplicator or imported from a previous version.

Solution: Use a Global Script C action on each OS client that triggers the horn programmatically via the WinCC API when an alarm of the target class arrives.

Step A - Create a Project Function

In WinCC Explorer on the OS client, navigate to Global Script → C Functions → Project Functions and create a new function:

// Function: TriggerHorn_AlarmClass
// Called from a global action on alarm arrival
void TriggerHorn_AlarmClass(char* lpszPictureName)
{
    // Play WAV from project Horn folder
    #pragma code("Winmm.dll")
    BOOL bResult;
    bResult = sndPlaySound("C:\\Program Files (x86)\\Siemens\\Automation\\WinCC\\WinCCProjects\\<ProjectName>\\Horn\\alarm.wav",
                           SND_ASYNC | SND_NODEFAULT);
    #pragma code()
}

Adjust the WAV path to match the local project path on the OS client. The SND_ASYNC flag returns immediately so subsequent events can re-trigger; SND_NODEFAULT prevents the Windows default sound from being used if the file is missing.

Step B - Create a Global Action

Navigate to Global Script → C Actions → Global Actions and create a global action that calls the project function on alarm events:

// Global action: triggered on every alarm message
#include "apdefap.h"

int gscAction(void)
{
    // Trigger horn for every incoming alarm
    TriggerHorn_AlarmAlarm();
    return 0;
}

Configure the trigger of this global action in the Global Script editor: set the trigger to OnMessage with the appropriate message class filter (for example, Alarm or Class.Alarm depending on the project schema).

Step C - Deploy to Clients

Save the project function and the global action on the engineering station, regenerate the OS client, and download to each client. Restart WinCC Runtime on the clients to activate the new actions.

7. File Path and Project Layout

On OS clients in a client-server topology, the Horn folder must exist locally on the client. The project duplicator normally copies it during project download, but if the folder is missing, manually copy the .wav file to the equivalent path on the client.

8. Troubleshooting Matrix

9. Verification Procedure

After configuration or workaround deployment, perform the following verification on every station that is expected to produce audible alarms:

1. Start WinCC Runtime on the target station.
2. Trigger a test alarm of the target message class from the Alarm Logging editor (right-click → Simulate Message) or via a forced tag value.
3. Confirm that the configured .wav plays on the station-local speakers.
4. For redundant topologies, force a failover (disable the Master network interface or stop the Master WinCC service) and re-trigger an alarm on a client. Confirm playback continues.
5. Inspect the Windows Event Viewer for WinCC Runtime errors relating to horn playback.

10. Related PCS 7 Documentation

For projects running PCS 7 V8.0 or later, the official Siemens Knowledge Base article How is the horn editor configured for single-user stations, servers, redundant servers and client OS stations in SIMATIC PCS 7 / WinCC? provides the canonical procedure with screenshots. The WinCC Information System installed with the engineering software also documents the Horn Editor under Options → Horn in the help index.