Circuit :-

555-Timers

We use two 555's to generate the 40KHz square wave and 200Hz square wave, the 40khz is required to excite the transmitter with its resonant frequency of oscillation and 200hz to modulate the 40khz wave so that our hands can feel the pressure point. 

                So basically Tlow for the first 555 producing 200hz is= 1/(2*200hz)=2.5 ms

so 2.5ms=0.69*R1*C, choosing C as 0.1uf, R1=36k ohms approx.In order to get symmetric wave the charging and the discharging time constant of the capacitor should be the same therefore R1=R2=36k ohms, and during charging from 5v source ,both R1 and R2 is in path of C, therefore we bypass R1 with a diode , now the during charging ,C charges only through R2 since the diode acting as short bypasses R1. 

                The same goes for The second 555 timer, except here Tlow =1/(2*40khz)=12.5us,so 

12.5us=0.69*R1*C, choosing C as 0.1uf, R1=180 ohms approx.

AD633

The square wave outputs from the two 555's are then fed into the inputs of AD633 analog multiplier ,which amplitude modulates the two waves, meaning, the amplitude of the carrier(40khz) is modulated with the 200hz wave.

MAX44250

This is an high precision,low noise,minimal dc offset 20V rail-rail op-amp with bandwidth of about 10Mhz well above the required 40Khz. The timers produce an output wave of 5Vp, we need to amplify this to about 20Vp in-order to attain maximum sound pressure level from the transmitters, therefore for non-inverting config 

                                              1+(Rf/Ri)=Vout/Vin, Vin=5Vp,Vout=20Vp,

Therefore 1+(Rf/Ri)=4,or Rf/Ri=3, therefore choosing Rf as 3K ohm and Ri as 1k ohm, we obtain the desired gain.

Clamper

Although the wave is alternating, yet it has a peak voltage of 20V rather than a peak-peak voltage of 20V with peak voltage of 10v, therefore we employ a clamping circuit to increase the negative dc bias, in other words we shift the positive 20V peak ,10V below ,so that we have 10V peak symmetric wave with 20Vp-p

where 'V' is 10V,

BJT Switch

The output from the clamper ,is then fed to the transmitter via a bjt switch monitored by the digital pins of the arduino. When the digital pins are high, they forward bias the p-n junction between the base and emitter respectively therefore allowing collector voltage to reach the emitter or the transmitters.

Finished Circuit, haven't included the base and collector resistance for the transistor due to lack of
clarity, however they must be added or else the 5v supply from the digital pins of arduino will fry the transistors