The main parts of this device are a shunt transformer with exciter winding and regulating winding, a series transformer with a booster winding and a series winding, and an on-load tap-changer with which it is possible to regulate the phase-shift introduced by the PST. The line voltage at Node 1 is applied to the exciter winding of the shunt transformer and transformed to the regulating winding according to the turns ratio. With the on-load tap-changer it is possible to extract a portion of the regulating winding voltage and feed it into the booster winding of the series transformer. The voltage applied to the booster winding is then transformed to the series winding according to the turns ratio. The combination of Y-connected regulating winding and the delta-connected booster windingage is given in weeks after birth.

### Parent characteristics {#s2b6}

For the parents, five characteristics were coded: whether mother or father completed the questionnaires, the age of the mother at birth, the number of years of education of the mother at birth, ethnicity of the participating parent, and socioeconomic status (SES) of the family. Parental stress scores were coded separately for mothers and fathers, in order to compare the two. The mean age and years of education of the mother at birth in the sample were coded in whole years. Ethnicity of the participating parent was coded twofold, first the exact ethnicity of the parents was coded as a string variable, and, secondly, whether the ethnicity of the parents represented a majority or minority in their residing country was