Extech older power supplies - how does master/slave linking work?

[dobsonr741]

I got an Extech 382260 power supply recently. Also sold as Voltcraft LSP-1403, Maplin N27GG, Manson SSP-7080. Great little form factor. It has a master/slave linking mode. I'd like to find out how it works with only GND + 1 wire going between master and slave. I see no analog voltage or any digital signaling leaving the master. Would be great to put the box in remote mode and control it's voltage externally. Does anyone know how?

[dobsonr741]

Looked further. The master presents a voltage proportional to the output current. I expect the master to cut back on it when the feedback loop want to reduce the output voltage. Anyone experimented with controlling a slave?