Here are some key features and specifications of the Fluke 1503 Insulation Resistance Meter:

1. Insulation Resistance Testing: It can test insulation resistance up to 2000 MΩ.

2. Test Voltages: It typically offers selectable test voltages of 500 V and 1000 V.

3. Voltage Detection: The Fluke 1503 can measure AC/DC voltage up to 600 V. This is important to ensure that no voltage is present before starting insulation tests, for safety reasons.

4. Safety Ratings: The device adheres to safety standards, ensuring it's safe to use in various environments.

5. Auto-discharge: The meter's auto-discharge function ensures that capacitive voltage is released after a test for user protection.

6. Remote Test Probe: A feature that can save time, as you can press the test button once and repeat tests without coming back to the meter.

7. Display: It comes with a large, easy-to-read display with backlight, facilitating work in low light conditions.

8. Durability: Like most Fluke instruments, the Fluke 1503 is built rugged for field use.

9. Resistance Measurements: Apart from insulation resistance, it can also measure resistance up to 2000 Ω.

10. Battery Life: Typically offers a long battery life for extended use, reducing downtime.

11. Automatic Shut-off: To conserve battery life, the device usually shuts off after a certain period of inactivity.

The Fluke 1503 Insulation Resistance Meter is a valuable tool for electricians, maintenance teams, and other professionals who routinely inspect and maintain electrical systems.