690 
# ee 
while the other 6AG7 is driven to full current, Use of the Step Duration 
Flip=flop [see Sec. 3(a)] to drive the 6AG7 stage insures a sharp voltage 
change and provides a means for controlling the duration of the step func- 
tion, 
The operation is initiated by the closing of an external switch or by 
an internal oscillator, The pulse, so derived, trips the Time-delay Flip- 
flop which, on the initial flip, produces a pulse for actuation of the ex- 
ternal recording mechanism, and on the return flop provides the pulse for 
tripping the Step Duration Flip-flop. The time delay between pulses may be 
adjusted over the range 100 psec to 2 sec, 
The output covers a range from 5 mv to 2 volts in four decades, Be- 
Sides the step function, provision is also made for the generation of ex- 
ponentially decaying functions of 50-, 150-, and 500—psec time constant, 
through use of an R-C circuit, 
For field calibrations a circuit is provided to check the standard 
voltage output at one point against a 1g-volt dry cell, The battery net- 
work is preadjusted to give 4 convenient fixed voltage; this is connected 
through a series resistance and switch to a point of presumably equal voltage 
on the standard voltage ranges On closing the switch, any difference in the 
two voltages appears across the series resistance in a step form. Amplified 
in a condenser-coupled amplifier and viewed on an external oscilloscope, 
the voltage difference appears as an exponentially decaying function. A 
small adjustment of the battery valtage is provided for estimation of small 
differences in voltage. 
The main difficulties encountered with this circuit have been in select- 
ing the VR tubes and in combating leakage problems. Since the B+ is grounded 
to obtain positive direction of the step, considerable care must be taken to 
prevent leakage to the high-impedance grid circuits from affecting the opera- 
tion, particularly that of the flip-flops. Care in wiring will eliminate 
most of this, howevere 
Four units of this type have been in calibration use for over six months, 
and aside from the difficulties mentioned, have given excellent service. 
Se Time standards 
For calibration of the time scales, an accurate, reliable, and easily 
calibrated time standard is required; an output wave form easily measurable 
