Two dual-output, mobile communications dc sources are available for optimizing of testing of digital cellular phones, chargers and other battery-powered devices. The HP 66309B and 66309D dc sources provide two outputs for testing both the main battery power and battery-charging circuitry. Designers can test phones and chargers with the same piece of test gear. As a result, users save rack space and eliminate the need for two separate power supplies. Each source features 5A peak current with 15V main output capability and 2.5A peak current with 12V secondary output capability. Excellent voltage transient response ensures maximum test throughput by minimizing device shutdowns resulting from significant voltage drops in the test wiring. The units are identical except for the D version's addition of a built-in DVM.