Despite the performed progressive research work, the interpretation of negative group delay (NGD) function remains not familiar to non-specialist design and fabrication circuit engineers. The functionality misunderstanding limits the NGD circuit applications compared to other classical electronic functions. The present paper is dealing on the design of tunable property circuit by operating with positive and negative delay behaviors. The topology of the tunable circuit by using low-pass (LP) type NGD one is described. The design formulas for calculating the circuit resistor and capacitor parameters from the desired delay are expressed. The design feasibility of the tunable circuit composed of LP-NGD cell and RC-circuit is validated with a proof-of-concept (PoC) implemented on a test board. Two different signals with pulse and arbitrary waveforms having tens-milliseconds duration were considered during the validation tests. As expected by tuning a varistor from 0.4 kΩ to 1 kΩ, the negative delay behavior varying from about -0.4 ms was verified thanks to the time-advanced effect due to the LP-NGD property. Then, the output signal delay was observed to become positive when the varistor is tuned from 1 kΩ to 3 kΩ.