vp1a p1a 0 pulse ( 0 pwra td tr tf 'tp/2-td1-td2-tr' tp ) vp1na p1na 0 pulse ( pwra 0 td tr tf 'tp/2-td1-td2-tr' tp ) vp1da p1da 0 pulse ( 0 pwra 'td' tr tf 'tp/2-td2-tr' tp ) vp1dna p1dna 0 pulse ( ...