The Measurement of the Electric Activity of the Olfactory Bulb in Free Swimming Carp (Cyprinus Carpio L.) by Underwater Telemetry Systems

A direct-wired telemetry system and a radio telemetry system were constructed in an attempt to measure the electric activity of the odfactory bulb in free swimming carp. The direct-wired telemetry system had a long, flexible, insulated signal wire, a high-gain ac amplifier, and a recording instrument. The radio telemetry system consisted of a transmitter which employed a single-channel pulse-frequency modulation (PFM)/FM and a receiver which contained a commercial phase-locked FM tuner, a frequency-voltage converter, a low-pass filter, and a recording instrument. The main specifications of the transmitter were as follows: main carrier frequency, 78 MHz; subcarrier pulse frequency, 2.5 kHz; input impedance, 2 ×107 ¿or more; dynamic range of input, 0.01-3.00 mV; weight, 3.2 g in water; working life, about 50 h when supplied by two silver oxide cells of 1.5 V, 75 mA/h; working range, 3 m in city water. The overall frequency characteristic of the radio telemetry system was 0.24-74 Hz (¿3 dB). By means of these telemetry systems, the first satisfactory records of electric activity were taken from the olfactory bulb in free swimming fish.