diff --git a/hosts/telefonmann/default.nix b/hosts/telefonmann/default.nix
index 4e1eb72..338d6cc 100644
--- a/hosts/telefonmann/default.nix
+++ b/hosts/telefonmann/default.nix
@@ -147,6 +147,7 @@ in {
 
     extensions = {
       "*99" = { mode = "page"; displayName = "Durchsage an alle"; };
+      "*100" = { mode = "all"; displayName = "Alle rufen"; };
       # custom app extension example:
       # "*00" = { mode = "app"; displayName = "Echo test"; app = "Echo()"; };
     };
diff --git a/modules/voip/asterisk/default.nix b/modules/voip/asterisk/default.nix
index f92c232..661d6b3 100644
--- a/modules/voip/asterisk/default.nix
+++ b/modules/voip/asterisk/default.nix
@@ -281,9 +281,9 @@ let
 
     # Page and app extensions from cfg.extensions
     + "\n" + lib.concatStringsSep "\n" (lib.mapAttrsToList (ext: extCfg:
-        if extCfg.mode == "page"
-          then "exten => ${ext},1,Page(${allPageEndpoints},i,120)"
-          else "exten => ${ext},1,${extCfg.app}"
+        if      extCfg.mode == "page" then "exten => ${ext},1,Page(${allPageEndpoints},i,120)"
+        else if extCfg.mode == "all"  then "exten => ${ext},1,Dial(${allL2Endpoints},30)"
+        else                               "exten => ${ext},1,${extCfg.app}"
       ) cfg.extensions)
 
     # Auto-generated intercom extensions
diff --git a/modules/voip/dashboard.nix b/modules/voip/dashboard.nix
index 5b7d43a..94b6fd5 100644
--- a/modules/voip/dashboard.nix
+++ b/modules/voip/dashboard.nix
@@ -331,7 +331,9 @@ let
           <table>
             <tr><th>Extension</th><th>Name</th><th>Type</th><th>Detail</th></tr>
             ${lib.concatStringsSep "\n" (lib.mapAttrsToList (ext: extCfg:
-              let detail = if extCfg.mode == "page" then "all phones" else extCfg.app; in
+              let detail = if extCfg.mode == "page" then "all phones"
+                           else if extCfg.mode == "all" then "all shared-line phones"
+                           else extCfg.app; in
               ''<tr><td><code>${ext}</code></td><td>${extCfg.displayName}</td><td>${extCfg.mode}</td><td><code>${detail}</code></td></tr>''
             ) cfg.extensions)}
             ${lib.concatStringsSep "\n" (map (ic:
diff --git a/modules/voip/options.nix b/modules/voip/options.nix
index 68c6245..644c08a 100644
--- a/modules/voip/options.nix
+++ b/modules/voip/options.nix
@@ -315,12 +315,13 @@ in {
       type        = lib.types.attrsOf (lib.types.submodule {
         options = {
           mode = lib.mkOption {
-            type        = lib.types.enum [ "page" "app" ];
+            type        = lib.types.enum [ "page" "all" "app" ];
             default     = "page";
             description = ''
               Extension mode:
-              - "page": one-way announcement to all phones
-              - "app": custom Asterisk dialplan application
+              - "page": one-way announcement to all intercom-capable phones
+              - "all":  two-way call ringing all shared-line phones (allL2Endpoints)
+              - "app":  custom Asterisk dialplan application
             '';
           };
           displayName = lib.mkOption {
diff --git a/modules/voip/provisioning/directory-json.nix b/modules/voip/provisioning/directory-json.nix
index 6b899bd..9f99fd8 100644
--- a/modules/voip/provisioning/directory-json.nix
+++ b/modules/voip/provisioning/directory-json.nix
@@ -8,8 +8,9 @@ let
 
   personContacts = lib.mapAttrsToList (_key: person:
     lib.filterAttrs (_: v: v != null) {
-      displayName = person.displayName;
-      extension   = person.extension;
+      displayName   = person.displayName;
+      extension     = person.extension;
+      sipUsernames  = lib.attrNames person.phones;
       intercomExtension =
         if cfg.intercomPrefix != null && extensionHasIntercom person.extension
           then "${cfg.intercomPrefix}${person.extension}"
@@ -19,10 +20,11 @@ let
     }
   ) cfg.persons;
 
-  sharedPhoneContacts = lib.mapAttrsToList (_key: phone:
+  sharedPhoneContacts = lib.mapAttrsToList (key: phone:
     lib.filterAttrs (_: v: v != null) {
-      displayName = phone.displayName;
-      extension   = phone.extension;
+      displayName  = phone.displayName;
+      extension    = phone.extension;
+      sipUsernames = [ key ];
       intercomExtension =
         if cfg.intercomPrefix != null && models.${phone.model}.hasIntercom
           then "${cfg.intercomPrefix}${phone.extension}"