A pleating apparatus comprises a support surface, first and second pleating surfaces, and a driver for compressing a portion of a filter material between the first and second pleating surfaces to form a pleat, where at least one of the pleating surfaces is curved or extends at an acute angle with respect to a support surface. The driver and the encoder are coupled to the light source so that the light source produces a modulated light signal in accordance with a predetermined signature. The crystal nucleating agent is preferably trisamides of trimesic acid or trisamides of trimesic acid, and the thermoplastic resin is preferably a lactic acid resin and more preferably a polylactic acid. A drive shaft of the clutch actuator extends in the vertical direction. It can be verified, based on the assigned serial numbers, that each frame in the first set has been sent to the remote network element prior to sending frames in the second set. The absolute gravimeter is moved periodically to the location of each relative gravimeter to measure absolute gravity.