DESCRIPTION OF THE SHOCKER 



The Bureau of Commercial Fisheries Type 

 IV shocker^ weighs 9 kg., excluding abattery, 

 and measures 15 by 30 by 20 cm. (fig. 1). The 

 schematic diagram of the Type IV shocker is 

 shown in figure 2, The 12 volt (v.)/400-v. dyna- 

 motor output is connected in parallel with a 

 100 microfarad (/jf.), 600-v. capacitor bank 

 to provide power for the shocker. In operation, 

 this supply is connected on one set of normally 

 open contacts of a mercury-wetted relay, 

 capable of operating up to 100 pulses per 

 second. The other side of the normally open 



'- Some of the materials and methods described here, we 

 credit to Richard B. Thompson, Fishery Biologist, Bureau 

 of Commercial Fisheries Biological Laboratory, Seattle, 

 Wash. His foresight led to the development of the Bureau 

 of Commercial Fisheries shockers to Type I, II, and III, 

 which provided the basis for development of the Type IV 

 shocker. 



contacts of the relay is connected to the 2- 

 ampere (a.) fuse, power output plug, and cable 

 to the anode. The mercury-wetted relay is 

 driven with an OA4G relaxation oscillator 

 which, when fired, energizes the coil of the 

 relay. Duration of the output pulse is fixed by 

 the size of the capacitor in the power supply 

 side of the mercury- wetted relay coil. Fre- 

 quency is determined by the time constant of 

 the selected capacitance and fixed resistance 

 in the trigger anode circuit of the OA4G 

 thyratron. Frequencies of 20 to 75 pulses per 

 second with a duration of 6 milliseconds 

 (msecs.) are easily obtained with this circuit. 

 A power switch located on the front panel, 

 when in the "on" position, connects the dyna- 

 motor to a 12-v. battery. With the local- 

 remote switch in the local position, the unit 

 operates continuously. With the switch in the 

 rennote position, the dynamotor operates only 

 when the strip-switch on the anode handle is 

 closed. The strip-switch energizes the coil 



Figure 1. — The Type IV shocker in operational condition, less the cathode. The strip-switch mounting Is on the 

 anode handle. The small black box on the shocker is the running-time meter. 



