pe substantially achieved with the arrangement of Figure 2.4, if stable precision film resistors and stable bias batteries of low internal impedance are employed. The values of R,, R,, and R, shown in Figure 2.4 include estimated diode incremental reaiatances of 290, 270, and 100 ohma, respectively. Static calibration of the circuit was impossible, because of dissipation difficulties. Pulse calibration, which was tedious at best, gave results so near to the calculated values that calibration by calculation was employed. The relevant equations are given below: V=RUI, ford0<V<V, V=V;,+Ral, for Vy < V< Vy, and Rg = parallel resistance of R, and Ry. V =V;+Ryl, for V; < V < V3, and Ry = parallel resistance of R,, R,, and Ry. V =V3 + Rol, for V3 < V < 60, and Ro = parallel resistance of R;, R,, Ry, and Ry. Actually, only calculations for the points V =0, V = V,;,V = Vy, V = V3, and V = 60 need be made, since the circuit is linear between these points. The calculated response of the two Log-R's employed is shown tn Figure 2.5. A converter (HFC) is used in all four detector channela to change relatively slowly varying direct current signals, unsuitable for magnetic recording, to frequency-modulated square-wave information. The circuit of a typical converter, excluding the succeeding binary used for wave shap- ing, ia shown in Figure 2.6. Tubes VTi and VT2 are in a direct-coupled regenerative loop. A signal voltage applied to the input terminals causes a changing current to flow into Capacitor C, raising the grid potential of VT1 in a substantially linear fashion. This tube is normally cut off, since VT2 tends to be heavily conducting. After a time the grid voltage of VT1 rises above cutoff and a rapid regenerative action forces VT1 to conduction and VT2 to nonconduction. The relatively large plate-load resistor (R, = 100k) for VT1 causes the bias current now flowing in Ry to be smaller than before. The resulting low bias on VT1 causes the grid of that tube to be positive with respect to its cathode. A rapid partial discharge of capacitor C occurs and the tubes then revert to their initial conduction atates. The action then repeats, generating a sawtooth wave across C. The frequency tends to be proportional to signal voltage. Short positive pulses are taken from the plate of VT2 for triggering a wave-ahaping binary. A typical calibration ig shown in Figure 2.7. A small current is ordinarily fed to Capacitor C from the plate supply to maintain a atandby oscillation during no-signal conditions. Resistor R, is varied to adjust the respo.ise to a desired range. Regulated supplies and stable components are essential. The Cal detector (Detector 1), in addition to its gamma-ray-measuring function, also provided a trigger pulse, which initiated a timing sequence. The Cal detector gate pulse and the Lil gate pulse (See Figure 2.3) generated here are added and recorded on tape 21