There is a device: lights and ringtone activator ref. 2438 that is used for this.

This device can be used in installations that require high voltages when receiving a call. This equipment may activate a ringtone, a siren or light when the street panel´s call button is pressed.

Small, they are easy to install in electrical cabinets. They can be fitted inside a standard 10x10 cm box. They have adhesive strips for fastening, or can be screwed directly to the wall.

There are 2 terminals in the VDS telephones and monitors (depending on the models, dedicated for the connection of this device.