1369162 Radio receivers; transducers; horns MOTOROLA Inc 19 Dec 1972 [10 Jan 1972] 58531/72 Headings H3Q H4J and H4X [Also in Divisions A3 and H1] In a radio receiver including a rectangular housing having an interior partition wall 18, Fig. 4, separating first and second rectangular elongate compartments 11, 12, the second compartment 12 has a passage 50, 53, 51, Fig. 7 forming an acoustical horn, a removable radio receiving means 25, 26, Fig. 2, including transducer means 29 for converting electrical waves to sound waves is receivable in the first compartment 11 and an acoustical chamber 34 is secured in the first compartment 11 in communication with the acoustical horn 50, 51, 53 and the transducer means 29 for coupling the transducer sound waves to the acoustical horn for amplification and emission at 17. The radio receiving means 26 and transducer housing 29 are mounted on a printed circuit panel 25 so as to be removable from the compartment 11. The transducer housing 29 includes a transducer (35, Fig. 10, not shown) coupled by a spiral passage (32) to an output aperture 30. When the radio receiver 26 and the transducer 29 are inserted into the compartment 11 the transducer output aperture 30 engages a rubber cylinder 33 which is attached by a groove (42, Fig. 9, not shown) to the walls 38 of an input aperture of the acoustical chamber 34. The sound output from the transducer 29 is passed via a spiral conduit (46, Fig. 8, not shown) in the acoustical chamber 34, an output aperture (44) of the chamber 34 and an aperture 45 in the partition wall 18 to the hyperbolic acoustical horn 50, 53, 51 for emission at an aperture 17 in the top wall 13 of the radio receiver which may be a radio pager or a transmitter-receiver. The housing has a clip 19 for attaching to the user's shirt pocket or belt.