258,235. Florisson, C. L., and Soc. de Condensation et d'Applications Mecaniques. Sept. 8, 1925, [Convention. date]. Bearings and distances, determining. - Supersonic submarine signalling-apparatus combined in some cases with wireless signalling apparatus, is used for navigation purposes for determining the relative bearing of, and the distance between, two ships or a ship and a shore station; and the submarine signalling system may be used alone for depth-sounding or distanceindicating by the echo or forward and return method. The direction of a sending station is first determined by ordinary radiogoniometric apparatus, .and the submarine signalreceiver is then oriented in the determined direction. The direction may be verified, or mav be initially ascertained, by the sumbarine signal receiver. A simultaneous radio and submarine signal emitted by the sending station is then received consecutively by the receiving instruments, and the time interval between them is measured, thus giving a direct indication of the distance. Determining distance by time interval between signals in different media. The apparatus and circuits of Fig. 14 are utilized as follows. The radio signal is transmitted by the leads 28. 29 from the aerial, through a switching apparatus 36 to the receiver 27, causing a direct current impulse to flow from the terminals 40, 41 through a hand-switch 43 (which is closed), contact 45 of a reversing relay 44, relay coil 61, contacts 79, 80 of a change-over switch 71, contact 46 of relay 44 and push-button switch 55, 58. The contacts 63, 64 are thus closed, and a battery circuit is completed through the relay coil 50 and a coil 66-for starting the clock 67, the handswitch 68 being in position to bridge contacts 69. The coil 50 attracts its core and draws down the rod 49 at a rate retarded by the dashpot 51. After an interval, the slots 88, 89 in the rod 49 engage pins on the reversing-switch arms 45, 46, and reverse the connections between the leads 28, 29 and the coil 61. As the radio signal has now ceased, the arm 63 remains on the contact 64, the coil 50 remains energized, and the clock 67 continues in action. The submarine signal is now received on the leads 28, 29 and in the receiver 27, and another impulse is sent in the reverse direction through the coil 61. The lifting of contact 63 opens the battery circuit, thus stopping the clock 67, and releasing the rod 49 which is returned quickly to normal position by its spring 53, the dashpot being inoperative during the return stroke. Should the signals be too weak to operate relay 61, the operator may listen to the signals in a circuit closed by the switch 42, and may send a pair of successive direct-current impulses from the battery 60 through the coil 61 by manually operating the push-switch 56. These impulses reverse the switch 44 and start and stop the clock 67 in the manner described above. Determining distance by time interval between forward and return signals or between signal and echo. Assuming that the station shown in Fig. 14 is to send the forward signal and receive the return signal, the switch 68 is thrown on to contacts 69. and the forward signal is sent by depressing the push 75, which is arranged to throw over both arms 55, 73 of the switch 54. The upper arm 73 closes a battery circuit connected to terminals 15, 16 of the switching- apparatus 36, and causes the transmitting generator 26 to send a signal through the leads 28, 29 to the submarine signal-emitter. The lower arm 55 closes the circuit of the battery 60 through coil 61, which as before starts the clock 67 and throws the reversing-switch 44. When the return signal or echo is received in the leads 28, 29, it passes reversely through the coil 61, stops the clock 67 and restores the reversing-switch 44. If the station of Fig. 14 is to receive the forward signal, and to send the return signal, the switch 68 is thrown over to contacts 70, so that an incoming signal energizes the coil 72. The core and rod 83 are attracted, unimpeded by the dashpot 82, and the slots 85, 86 engage the pins on the switch arms 76, 79. On account of the different lengths of the slots, the contact 80 is first opened to de-energize the coil 61, the contact 77 is next closed to cause the return signal to be sent out, and the contact 81 is then closed to send a reverse current from the battery 78 through the coil 61, thus de-energizing the relay coil 72. The rod 83 is now slowly returned to normal position, retarded bv the dash-pot 82, the contacts being made and broken in the reverse order. Conjoint transmission and reception of wireless waves and supersonic submarine signals. Although the frequencies employed for the wireless signals are not necessarily identical with those used for the submarine signals, the Specification describes several methods for energizing the two signal-transmitters from the same highfrequency source 26, and for transferring the received signals to the same amplifying-receiver 27. In the example shown in Fig. 5, the leads 28, 20 are connected to tappings on a coil, which has other taps connected respectively to the submarine signal device a which may serve both as transmitter and receiver, and to the transmitting. and receiving aerial a. A variable condenser is interposed in the aerial tapping, and a tuning- coil is connected between the aerial and earth 98. Alternatively, the leads 28, 29 may be connected to the aerial coil as indicated in dotted lines. Other arrangements comprise conductive and inductive couplings, between the leads 28, 29 and the two signal devices; and arrangements for using a frame aerial instead of the non-directive aerial c are also described.