Garmin GPS 120 User Manual

The Garmin GPS 120 is a rugged, waterproof marine GPS receiver designed for navigation. It features a high-contrast LCD display, simple keypad interface, built-in worldwide basemap, waypoint and route storage, NMEA 0183 output, and operates on 4 AA batteries or external 12V DC power. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

Features at a Glance

Key components: Waterproof case, LCD display with backlight, Keypad, External antenna connector, Power/Data cable port, Battery compartment.

Installation

Unpack and inspect contents. Choose a suitable mounting location.

1. Mount the unit: Use the included bracket to mount in a location with clear sky view.
2. Connect power: Insert 4 AA batteries or connect the 12V DC power cable to a marine power source.
3. Connect external antenna (optional): Attach to the rear connector if needed for better reception.
4. Connect NMEA devices: Use the data cable to connect to compatible chartplotters or autopilots.

WARNING! Ensure mounting surface is secure. Route cables away from moving parts and heat sources.

First-Time Setup

Power on the GPS 120; follow initial prompts.

1. Acquire satellite signal: Place unit outdoors with clear sky view; acquisition may take several minutes.
2. Set language: In the SETUP menu, select ENGLISH (default).
3. Set units: Choose nautical miles/knots, statute miles/mph, or kilometers/kmh.
4. Set position format: Select Lat/Lon, UTM, or other coordinate system.
5. Set time: Configure local time and date format.

CAUTION! Initial satellite acquisition requires an unobstructed view of the sky. Be patient.

Specifications

• Receiver: 12 parallel channel GPS receiver.
• Update Rate: 1 second continuous.
• Accuracy: <15 meters RMS.
• Velocity Accuracy: 0.1 knot RMS steady state.
• Interface: NMEA 0183 version 2.0.
• Power: 4 AA batteries (approx. 20 hours) or 12-40V DC.
• Waterproof: IPX7 standard.
• Operating Temp: -15°C to 70°C.
• Dimensions: 15.2 x 7.6 x 5.1 cm.
• Weight: 0.34 kg with batteries.

Controls and Settings

Access menus via the PAGE and ENTER keys. Front Panel: POWER, PAGE, ENTER, GOTO, MARK, arrow keys.

Key Functions: POWER turns unit on/off; PAGE cycles through display screens (Satellite, Position, Navigation, Highway); ENTER selects/confirms; GOTO initiates navigation; MARK creates a waypoint.

Setup Menu: Language, Units, Position Format, Time, Alarms, System (Backlight, Contrast, Tones). Navigation Settings: Route Preferences, Off Course Alarm, Arrival Alarm, Anchor Alarm.

Connecting Devices

Power: Battery compartment or DC input jack. Data: NMEA 0183 output port.

1. Turn off GPS before making connections.
2. Match cable pins to port (refer to wiring diagram in manual).
3. Secure connections with provided screws or ties.
4. Configure NMEA output sentences in the SETUP menu if needed.

Tip: Use marine-grade, tinned wire for all external connections to prevent corrosion.

Navigation Basics

Basic navigation with waypoints and routes.

1. Create a Waypoint: Press MARK at current location, edit name/symbol, press ENTER.
2. Navigate to a Waypoint: Press GOTO, select waypoint from list, press ENTER.
3. Follow a Bearing: The Navigation page shows bearing, distance, speed, and time to destination.
4. Create a Route: In the Route menu, select "New", add existing waypoints as legs, save.
5. Follow a Route: Select route from list, choose "Navigate", press ENTER.
6. Track Back: Navigate back along your recorded track log.

WARNING! GPS is an aid to navigation. Always use in conjunction with proper charts, compass, and situational awareness.

Advanced Features

Man Overboard (MOB): Press and hold GOTO to mark MOB position and immediately begin navigation back to it. Alarms: Set anchor drag, off-course, arrival, and proximity alarms. NMEA Output: Output position, speed, and heading data to connected devices. Simulator Mode: Practice navigation indoors (disable for actual use).

Care & Maintenance

Rinse with fresh water after saltwater use. Clean case with mild soap and damp cloth. Do not use harsh chemicals or high-pressure sprays. Ensure battery compartment seal is clean and intact.

CAUTION! Do not open the case. There are no user-serviceable parts inside. Refer servicing to qualified personnel.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits. This device complies with part 15 of the FCC Rules. Operation is subject to the condition that this device does not cause harmful interference. Copyright © Garmin Ltd. or its subsidiaries. For support, visit www.garmin.com/support or contact your local Garmin dealer.

Troubleshooting

Reset: System > Master Reset (erases all user data).

Service: Contact Garmin Product Support or an authorized service center.