Abstract: Apparatus for indicating at a distance the onset of parturition in animals including a radio transmitter and a source of electrical power adapted to be secured to the pre-parturient animal and a rupturable assembly adapted to be mounted across the vaginal orifice of the pre-parturient animal. The rupturable assembly has a preferred rupture line along which the assembly ruptures when the vaginal orifice distends during the onset of parturition. A switch, for connecting the transmitter to the source of electrical power, is secured to the rupturable assembly on one side of the preferred rupture line. A magnet holds the switch open while the rupturable assembly is unruptured in order to prevent the closing of a circuit between the transmitter and the source of electrical power. The magnet is secured to the rupturable assembly adjacent the switch but on the opposite side of the preferred rupture line therefrom. The switch is closed except when in close proximity to the magnet.