Abstract: A fixing member is inserted under pressure into a central hole of an ultrasonic vibrator, a case and a center axle are fixed by a screw, a bearing is fixed on an end portion of the center axle, a rotor is mounted to rotate by the bearing, a connection member is fixed to the rotor, projections are formed on the edge of a disk of the connection member, spaces are formed between the projections respectively, a contact member is composed by inserting ends of divided parts into spaces of the connection member, and a ring-like elastic member is mounted on the contact member which is pressed on the ultrasonic vibrator.

Abstract: Fish sonar signals, temperature signals, PH signals or speed signals of a boat which are emitted from a transmitter as RF signals are respectively received in a wrist watch type receiver, and are displayed on a display device attached to a case of the wrist watch type receiver, whereby each fisherman can see the state of the sea by putting on the wrist watch type receiver to his wrist.

Abstract: A fish sonar buoy is stayed on the surface of the water apart from a boat or shore, ultrasonic signals is emitted from a transmitter-receiver in the water, ultrasonic echo signals in the water are converted to electric signals in the transmitter-receiver, the electric signals are taken in a control circuit during a desired time after ultrasonic signals are emitted from the transmitter-receiver, and thus, a school of fish in the desired position below the water level is detected by a signal information device.

Abstract: A recording unit is disclosed which comprises a single hard wire member bent in the form of a coil, one end of which is a recording or current collecting end and the other end of which is a hook end. The coil support of an adapter supports the coil portion of the wire member. The hook end is hooked on one of the hook end supports of the arms extending from the adapter. The recording needle and the current needle are placed on their respective supports.