Abstract: A remote-controlled motor-driven drum is provided to wind and unwind a cord which holds a self-balancing sign carrier. The sign carrier, which has telescoping rails, is adjustable in width. Its center rail includes two sheaves to receive the cord and lead it from the drum back to an end secured to the ceiling. Thus, rotation of the drum serves to raise and lower the sign carrier and a sign carried by it. The sheaves on the carrier not only allow it to be raised and lowered, but also serve to make the unit self-balancingThe user attaches a sign to the carrier when it is in its lowered position and then raises the sign and carrier to the ceiling. The motor, which is reversible, is remotely controlled either by wires leading between the motor and a switch or by radio control (with a control similar to that used on a garage door).

Abstract: An acousto-optic apparatus is described that varies the time delay of electrical signals over a continuum of delays. In the preferred embodiment, a light source, which can be either coherent or incoherent, emits an optical beam that is focused into an acousto-optic cell. An input electrical signal is used to drive the acousto-optic cell which, in turn, modulates the focused optical beam. Portions of the input optical beam are modulated and diffracted at angles proportional to the frequencies and phases contained in the input electrical signal. By appropriately choosing the cone of angles at which the light is focused into the acousto-optic cell, the diffracted optical beam can be made to overlap with portions of the undiffracted, unmodulated optical beam. All of the light exiting the acousto-optic cell is then collected onto a device for detection. Optical photomixing of the diffracted beam and the undiffracted beam is performed in order to derive the input electrical signal with a time delay.

Abstract: An acousto-optic correlator for wideband signals. The invention is defined by and relates to device in which a laser beam is split into two paths of a Mach-Zehnder interferometer arrangement. A first Bragg cell of which, modulated with a signal Re{S.sub.1 (t)exp(jw.sub.o t)}, receives the first beam that is reflected off a first flat mirror. A second Bragg cell of which, modulated with a signal Re{S.sub.2 (t)exp(jw.sub.o t)}, receives a beam that is reflected off a second flat mirror. The undiffracted light from both of the modulators is blocked. The diffracted light emitted from the first and second Bragg cells passes through first and second imaging lenses respectively. The two diffracted light beams are then combined with an angular separation between beams. The combined beam is incident upon a square-law detector array which is at the image plane of the imaging lenses. Due to the square-law detection process, terms of low frequency biases and complex correlation on a spatial carrier develop.