Abstract: An annunciator to indicate the presence of a truck on a weighing platform to a weigh station operator is disclosed. The apparatus includes a presence sensor operable in response to the weight of the truck on the scales. The sensor provides a signal to a discriminator circuit which, depending upon the length of the signal from the presence sensor, determines whether the truck is merely passing over the scales or has stopped on the scales to be weighed. The discriminator produces an output causing a signaling device to operate and indicate to the operator of the weigh station that a truck is on the scales and is ready to be weighed.