. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. REFERENCES by 3 stages of amplification in earthed emitter, of which two are acceptor- tuned by negative feedback through parallel T's. The tuned stages select the jR-component of the electrocardiogram, and pass it on to a distorting transistor which, working with practically no forward bias, delivers a positive pulse at the collector corresponding to the peak of each R wave. This is used to trigger the transistor equivalent of a cathode-coupled flip-flop (Figure ). Pulses of standard
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. REFERENCES by 3 stages of amplification in earthed emitter, of which two are acceptor- tuned by negative feedback through parallel T's. The tuned stages select the jR-component of the electrocardiogram, and pass it on to a distorting transistor which, working with practically no forward bias, delivers a positive pulse at the collector corresponding to the peak of each R wave. This is used to trigger the transistor equivalent of a cathode-coupled flip-flop (Figure ). Pulses of standard size thus derived are used to charge a -7 5 V. Figure capacitor via a buffer transistor. The capacitor is discharged by a meter, whose reading is therefore proportional to the rate at which R waves arrive. Wolfendale, Morgan and Stephenson^^ have reviewed the use of transistors as computing elements, and include a decade counting circuit. Blake and Eames^^ have described a frequency meter for the range 0 to 100,000 counts per second. The count rate is indicated on a meter having a linear scale. The device is sensitive to input pulses only 60 mV in amplitude, corresponding to a current of 12 ^A. The accuracy claimed is ±1 per cent. REFERENCES 1 Bardeen, J. and Brattain, W. H. Phys. Rev. 74 (1948) 230 2 Cocking, W. T. Wireless World 61 (1955) 500 3 Oakes, F. Wireless World 61 (1955) 164 * Stuart-MoNTEiTH, G. Electron. Engng. 28 (1956) 544 ^ Jones, D. D. and Hilbourne, R. A. Transistor Amplifiers London; Iliffe « George, R. E. Proc. Vol 7, No. 4 ' PoTOK, M. H. N. and Wales, R. A. McF. Electron. Engng. 11 (1955) 344 8 Johnson, G. Wireless World 61 (1955) 31 9 Neale, D. M. and Oakes, F. Wireless World 62 (1956) 530 1" Fleming, L. Electronics 30 (1957) No. 1 11 Moody, N. F. Electron. Engng. 28 (1956) 94 12 SuTCLiFFE, H. Electron. Engng. 29 (1957) 140 13 Burton, P. L. Electron. Engng. 29 (1957) 394 14 Johnston, D. L. Wireless World 60 (1954) 518 1^ Mullard
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