determinant of transfer function

i am studying control system i crossed this transfer function

H(jw)=(1-jw/1+jw)

now taking determinant of this

|H(jw)|=1

My question in what way the determinant is usefull to learn about the systrem.Here the determinant of transfer function is 1,so the 1 saying anything about the system

Ussually we call that operation "taking the magnitude" rather than "taking the determinant".

The magnigude of H(jw) tells the magnitude response for sine waves driving the system. A sine wave drives the input and another sine wave with a partiular magnitude and phase comes out. |H(jw)| tells the ratio of magnitudes as output over input. A magnitude response of 1 is an all-pass filter. That filter might modify the phase of the output, but the magnitude is unalterred.