. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. SINE WAVE OSCILLATORS Modern crystal oscillators Crystal oscillators of the type so far discussed are primarily intended for radio work and the frequencies of crystals suitable for such circuits are rather high to be of direct use as timers in electrophysiological circuits. Thus it was at one time usual to employ 100 kc/s crystal oscillator and 'count Mean anode current. Suitable working point I Crystal frequency Figure Frequency to which anode circuit is tuned down' 10 times to prod
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. SINE WAVE OSCILLATORS Modern crystal oscillators Crystal oscillators of the type so far discussed are primarily intended for radio work and the frequencies of crystals suitable for such circuits are rather high to be of direct use as timers in electrophysiological circuits. Thus it was at one time usual to employ 100 kc/s crystal oscillator and 'count Mean anode current. Suitable working point I Crystal frequency Figure Frequency to which anode circuit is tuned down' 10 times to produce 10 kc/s (100 /^sec marks), count down 10 times again to produce 1 kc/s (1 msec mark) and so on. Since marks are seldom required at 10 [xsqc intervals, it is wasteful to produce an unnecessarily high frequency such as 100 kc/s and then have to cut down 10 times before pro- ducing a useful frequency. Modern four-terminal crystals such as the Standard Telephone and Cable 4023 can be had which oscillate at frequencies as low as 4 kc/s. The circuit recommended by Standard Telephones for crystal oscillators of this type is given in Figure The feedback path is lOk^Sg^F ^^^^ STC type A023. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Donaldson, Peter Eden Kirwan. New York, Academic Press
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