The Twin Stabilised D.C, Supply PP3 is a portable instrument providing two independent and floating stabilised d.c. supplies, each variable from 0 to 3ÖV at 1A maximum. The two supplies can be used separately, or connected in series lo provide a maximum output of 60V at 1A. In both sections of the instrument, the range is covered in three overlapping nominal 10V steps, with fine adjustment provided by a variable control directly calibrated in volts. A voltmeter and a dual-range ammeter are provided, and these can be switched independently to monitor either section. Both sections are provided with four terminal output networks which virtually eliminate the effect of resistance in the connecting leads to the load. Overload protection is effected by an electronic circuit which affords complete protection against both progressive and sudden short circuit overloads. This circuit is reset from the front panel by operation of the on/off switch. The instrument will operate from a.c. supplies of 90 to 130V and 200 to 240V. Fuses are provided to protect against both supply surges and internal component failure. The Twin Stabilised D.C. Supply PP3R is a 19-inch rack mounting version of the PP3. The specification is identical to the PP3 but the PP3R has the additional facility of the output being available on a 10-way terminal block at the rear of the instrument.