A valve device for a pneumatically-operated vehicle brake system can adjust the pneumatic brake pressure that can be fed to a brake in a controlled manner. A first variant of the valve device is configured as a modulator for use in an electronically regulated embodiment of the brake system; and a second variant is configured for use in a pneumatically controlled embodiment of the brake system. However, both variants have pneumatic interfaces and mechanical fastening points that are configured substantially identically with respect to one another to facilitate conversion of the brake system from one such embodiment to another.