the prior art mass controlled anti - g valve as illustrated in fig1 and having the characteristics illustrated in fig2 is modified by removing the upper spring chamber 19 as shown schematically in fig3 . in place of the upper chamber 19 ( fig1 ), a servo control , motor actuated , valve operating system 41 , as illustrated in fig4 is attached to the conventional lower body 11 . the motor 42 , through reduction gear train 43 , drives the cam 44 causing the seat 45 to cover and depress the pilot port 15 as the mass - spring combination 13 and 18 did in the conventional device . ( the air flow through the lower body 11 is the same in embodiments of the invention as in the prior art system , only controlled through movement of pilot port 15 in a new and unique manner .) a second motor 46 is driven by motor 42 and functions as a closed - loop motor - driven servo system . the motor 42 is actuated in response to a conventional accelerometer transducer 51 and a conventional pressure transducer 52 through an electronic control circuit as illustrated in fig5 a , 5b , and 5c . amplifiers 53 , 54 , and 55 are zero crossing detectors and have two discrete states at their outputs , + 9 v or - 9 v . they are used to switch transistors 56 , 57 , 58 , and 59 . five potentiometers , 60 , 61 , 62 , 63 , and 64 are adjustable on the control panel . they are labeled &# 34 ; ramp psi / g 0 - 5 &# 34 ;, &# 34 ; ramp onset 1 - 5g &# 34 ;, &# 34 ; step onset 1 - 5g &# 34 ;, &# 34 ; step psi 0 - 5 &# 34 ;, and &# 34 ; limit psi 6 - 11 &# 34 ;, respectively . switch 65 is a panel mounted pushbutton &# 34 ; test &# 34 ; switch and switch 66 is a toggel switch for inserting a &# 34 ; ready pressure &# 34 ; value . the effects of these controls will be discussed later . potentiometers 67 and 68 are balance controls for their associated pressure and acceleration transducers 52 and 51 respectively . the output of pressure transducer 52 is amplified by amplifier 69 and provides a voltage responsive to the ambient pressure exerted on transducer 52 to the summing amplifier 70 . potentiometer 71 provides a gain control of amplifier 69 . the output of accelerometer 51 is amplified by amplifier 72 . the gain of which is controlled by potentiometer 73 . it is normally set to provide an output of approximately 0 . 5 v / g ( volts per pounds per square inch gage ). the output voltage from the accelerometer amplifier is compared with that set by potentiometer 61 , the ramp onset level ( rol ), in amplifier 74 . when the output from amplifier 72 is greater than the rol the signal is passed through transistor 56 to amplifier 75 . the voltage appearing at the source of transistor 56 is the difference between the acceleration voltage and the rol voltage multiplied by the gain of amplifier 74 . this gain is varied from xo to x5 by adjusting potentiometer 60 , ( the ramp psi / g control ). ( the effects of varying potentiometers 61 and 60 are illustrated in fig6 .) amplifier 53 compares the acceleration voltage with that set by potentiometer 62 , the step onset level ( sol ), and when the acceleration voltage is greater , the voltage at the drain of transistor 59 , as set by potentiometer 63 , which represents step pressure ( sp ), is admitted through transistor 59 and resistors 76 to amplifier 75 . the effect of varrying sp and sol is illustrated in fig7 . spring loaded pushbutton &# 34 ; test &# 34 ; switch 65 is normally in the position shown . when the switch is actuated to the ground position an acceleration of 1g is compared with a zero set offset level and the valve responds to the step pressure setting on potentiometer 63 . it is to be noted that the step pressure must be set at greater than zero for any pressure value to be passed by transistor 59 when the test switch is operated , and that when it is operated a g voltage will activate transistor 59 to pass the step pressure voltage set on potentiometer 63 . amplifier 75 has a gain of x1 and its output is the total demand ( d t ) excluding the &# 34 ; ready pressure &# 34 ; input . the d t signal is applied at the drain of transistor 58 and through resistor 77 to the input of amplifier 55 . in amplifier 55 the d t signal is compared with the signal from potentiometer 64 which is applied through resistor 78 and represents &# 34 ; pressure limit &# 34 ; which typically is asjustable by potentiometer 64 on the control panel from approximately 6 psi to 11 psi . when d t is less than the set pressure limit p l , the signal at the drain of transistor 58 is admitted to amplifier 70 through resistor 79 . at the same time the signal at the drain of transistor 57 is blocked . when d t is greater than p l , amplifier 55 reverses , the signal at transistor 58 is blocked and transistor 57 admits the p l signal to amplifier 80 through resistor 81 where it is inverted and applied to amplifier 70 through resistor 82 . the input at resistor 82 is then a fixed voltage and causes the valve to maintain the selected pressure as long as it is less than d t . when d t decreases to a point below p l its signal is again admitted , p l is blocked and the valve follows d t . the input at resistor 83 is &# 34 ; ready pressure &# 34 ; ( rp ) and is controlled by operating switch 66 . the switch is shown in the drawing in the &# 34 ; off &# 34 ; position . when it is moved to &# 34 ; on &# 34 ;, the valve sees a demand of approximately 0 . 2 psi which just fills a typical anti - g suit volume , but is not uncomfortable to the wearer . it does , however , decrease inflation time significantly . the input at resistor 84 is the tachometer generator signal which serves to damp the response of drive motor 42 and prevent overshoot . the input at resistor 85 is an ac coupled input taken from the motor which aids to reduce oscillation or hunting to an insignificant value . the output of amplifier 70 drives transistors 88 and 89 through driver transistors 86 and 87 to operate the motor 42 ( forward , reverse , and stop ) in a conventional manner . motor 42 , tachometer 46 , amplifier 70 , and motor drive transistors 86 through 89 comprise a conventional feedback servo control system to drive motor 42 , actuating , through the gear and cam mechanism , the control rod 47 to move responsive to the electrical input signal at terminal 2 of amplifier 70 . potentiometers 90 , 91 , 92 , 93 , 94 , 95 , and 96 are conventional calibrating means for determining the range of the associated variable panel controls . accelerometer 51 is a conventional commercially available unit . an endevco model 2262 - 25 ± 25 is a suitable unit for use in embodiments of the invention . likewise , any suitable commercially available pressure transducer 52 , such as gould statham model pl 131tc ± 15 , is a suitable unit for use with the invention . the motor 42 and the motor 46 used as a tachometer generator are normally similar conventional permanent magnet field 12 vdc motors . the microswitch model 28 em 31 - ada - 1 is a suitable unit for both applications ( i . e ., motor and tachometer generator ). pressure transducer 52 through amplifier 69 provides a signal to summing amplifier 70 , through its respective resistor in the summing resistor bank connected to terminal 2 , to conventionally pressurize the garment responsive to decreased pressures at high altitudes independently of the pressurization of the garment due to acceleration forces . fig6 illustrates typical operation of the valve ( pounds per square inch suit pressure plotted against gravitational units of force ) for various settings of the rol ( ramp onset level ) 61 and the ramp psi / g 60 controls , with the sol ( step onset level ) 62 and the sp ( step pressure ) 63 controls set at zero . the lp ( limit pressure ) 64 is set at 11 psi and the rp ( ready pressure ) switch 66 is off . curve 101 illustrates the variation in suit pressure vs g with the ramp psi / g control set at 5 psi / g and the rol set at 0 . 2 g . for curve 102 the ramp was set at 4 psi / g and the rol set at 2g ; curve 103 ramp psi / g set at 3 and rol at 3 g ; curve 104 , ramp psi / g at 2 and rol at 4 g ; curve 105 , ramp psi / g at 1 and rol at 5 g ; curve 106 , ramp psi / g at 0 . 5 and rol at 5 g ; curve 107 , ramp psi / g at 0 . 25 and rol at 5 g ; curve 108 , ramp psi / g at 0 . 1 and rol at 5 g . with the ramp psi / g control set at 0 . 0 there is no buildup of pressure with increases in g and the valve response characteristic may be represented as merely a line 109 on the abscissa . it should be stated that the foregoing curves and the following illustrative curves were obtained from an operating embodiment of the invention on a centrifuge . a centrifuge of known characteristics provides an ideal means of calibrating embodiments of the invention . fig7 illustrates typical response characteristic of an embodiment of the invention showing suit pressure psi plotted against + g units , in which ramp psi / g control 60 is set at zero and the rol ( ramp onset level ) control 61 is also set at zero . the limit pressure control 64 is set at 11 psi and the ready pressure 66 is off . the step onset level ( sol ) control 62 is varied and the step pressure ( sp ) control 63 is varied providing the following characteristics as the gravitational force g is changed . in curve 110 , the sp is at 5 psi and the sol at 0 . 2 g ; curve 111 , sp at 4 psi and sol at 2 . 0 g ; curve 112 , sp at 3 psi and sol at 3 . 0 g ; curve 113 , sp at 2 psi and sol at 4 . 0 g ; curve 114 , sp at 1 psi and sol at 5 . 0 g ; curve 115 , sp at 0 . 4 psi and sol at 5 . 0 g ; with the sp set at zero the response characteristic is along the abscissa 116 . fig8 shows two response characteristics illustrating typical capabilities of embodiments of the invention . for response characteristic 120 the following parameters were set into the equipment . ramp psi / g control 60 set at 1 psi / g , ramp onset level control 61 set at 2 . 0 g , step onset level control 62 set at 4 . 0 g , step pressure control 63 set at 2 . 0 psi , limit pressure control 64 set at 7 . 0 psi , and the ready pressure switch 66 was on . various values of + g were then developed on the centrifuge and the corresponding suit pressures obtained . note , that with the ready pressure on , an initial inflation pressure of approximately 0 . 2 psi is maintained in the suit without any additional g force . this is shown at 121 . the parameters set in the invention for obtaining curve 122 are ; ramp psi / g , 1 . 4 psi / g ; ramp onset level , 4 . 4 g ; step onset level , 2 . 6 g ; step pressure 0 . 5 psi ; limit pressure 6 . 0 psi ; and ready pressure off . while the invention has been described as being particularly suited for multi - profile pressurization of aircrew anti - g garments in high performance fighter aircraft , it is to be understood that it is not so limited . those skilled in the art will readily apply the invention to those applications where flexible , precise pressure control is desired under varying ambient conditions of pressure and acceleration such as the testing of personnel and equipment on a centrifuge or in an altitude chamber or pressure chamber . unlike the prior art equipment where the acceleration sensor was physically part of and attached to the valve , embodiments of the invention are not so limited . the sensors do not have to be in or attached to the air line , but may be located at any desired location such as on a crew member , or even exterior the capsule .