The Keysight (formerly Agilent) 66309D dual output mobile communications dc source provides two outputs for testing both the main battery power and the battery charger circuitry, allowing customers to test phones and chargers with the same equipment. This feature helps save on rack space (2 outputs in a half rack box) and eliminates the need for two separate power supplies. Excellent voltage transient response ensures maximum test-system throughput by minimizing device shutdowns due to significant voltage drops in the test wiring. The 66309D dc source provides all of the capabilities of the 66309B with the addition of a built in digital voltmeter. The 66309D offers an Keysight (formerly Agilent)-developed feature that enables cellular-telephone manufacturers to detect permanently and intermittently open-sense wire connections automatically. Detection of open-sense wire connections allows users to prevent incorrect battery-charger calibration, incorrect test results and low-voltage phone shutdown due to a large transient voltage drop.