Linear F310 / Mighty Mule FM137 318MHz Digital Gate Keypad Technical Details
The Linear F310 / Mighty Mule FM137 is a programmable digital access keypad designed for compatible automatic gate operator systems. The keypad can be used as a wireless 318MHz access device with supported receivers or connected directly to compatible gate operator control inputs for hard-wired operation.
Linear currently identifies the professional version as model F310. FM137 is the Mighty Mule/GTO designation commonly associated with the same keypad family. Because these products have been produced across multiple operator and control-board generations, verify the exact model and installation method before using one designation as a direct replacement for another.
What This Keypad Does
The F310 / FM137 allows authorized users to activate an automatic gate by entering a four-digit PIN code. Up to 25 entry codes can be stored, allowing different codes to be assigned to family members, employees, service personnel, contractors, or other approved users.
Temporary codes can also be programmed to automatically expire after 1-7 days. This is useful for short-term access without permanently sharing the master or primary entry code.
Wired or Wireless Operation
The keypad supports both wired and wireless installation depending on the gate operator and control-board configuration.
- Wireless mode uses the keypad's 318MHz transmitter with compatible gate operator receivers.
- Hard-wired mode connects the keypad OUT and COM terminals to compatible gate operator control inputs such as CYCLE and COMMON.
- The 318MHz transmitter is disabled when the keypad is configured for hard-wired operation.
- Current FM137 documentation recommends keeping the keypad within approximately 50 ft of the receiver for wireless installations and testing range before permanent mounting.
Compatibility warning: A gate operator using a different frequency, receiver generation, radio format, or control-board input may require wired installation, a compatible external receiver, or a different keypad.
Compatible With
- Compatible LinearPro/GTO swing gate operators when supported by the operator control system
- Compatible LinearPro/GTO slide gate operators
- LinearPro GP-series operators in wired applications as specified by current Linear documentation
- Compatible Mighty Mule gate operators using supported FM137 programming or wired control inputs
- Mighty Mule MM371 and MM372 - current FM137 manual provides wireless programming instructions
- Mighty Mule MM571 and MM572 - current FM137 manual provides wireless programming instructions
- Mighty Mule MM271 and MM272 - current FM137 manual provides specific programming instructions and may require a DIP-switch transmitter during setup
- Select older GTO/PRO and Mighty Mule operators using compatible 318MHz receiver technology
- Other gate systems may use the keypad through a compatible hard-wired control input when electrical and control requirements are confirmed
Do not assume wireless compatibility with every Linear, GTO, Mighty Mule, Nice, garage door, or gate operator simply because the equipment has a radio receiver.
Features and Specifications
| Brand Family | Linear / GTO / Mighty Mule / Nice |
| Linear Model | F310 |
| Related Mighty Mule Model | FM137 |
| Product Type | Digital gate access keypad |
| Installation | Wired or wireless depending on operator |
| Wireless Frequency | 318 MHz |
| PIN Capacity | Up to 25 entry codes |
| PIN Length | 4 digits |
| Temporary Codes | Programmable for automatic expiration in 1-7 days |
| Battery Type | 3 AA batteries |
| Batteries Included | No |
| Wireless Range | Current FM137 manual recommends no more than approximately 50 ft from receiver; actual range varies by site |
| Wired Output | OUT / COM low-voltage control connection |
| Keypad Feedback | Illuminated keypad, status LED, and audible beeper |
| Incorrect Entry Protection | Approximately 40-second lockout after excessive unmatched key entries |
| Code Memory | Stored codes remain in memory if batteries lose power |
| Enclosure | Weather-resistant outdoor keypad housing |
Linear F310 vs. Mighty Mule FM137
The F310 is currently listed by Nice/Linear as the Linear digital keypad for LinearPro/GTO gate operator applications. FM137 is the Mighty Mule keypad designation. The products are commonly cross-referenced because they share the same basic 25-code wired/wireless access-control application.
Do not rely on the cross-reference alone when replacing an older keypad. Radio programming methods, operator receivers, control boards, and production generations have changed. Verify whether the installation requires an F310, FM137, newer Mighty Mule keypad, or hard-wired connection before ordering.
Temporary and Vacation Codes
The keypad supports temporary four-digit entry codes that can automatically expire after a selected period from one through seven days. This allows temporary access to be provided without deleting or changing permanent user codes after the visitor no longer needs access.
Wireless Compatibility Considerations
The FM137 uses a 318MHz radio transmitter in wireless mode. Some older systems use DIP-switch transmitter coding, while newer compatible Mighty Mule operators provide a learn procedure through the operator control board.
Frequency alone does not guarantee compatibility. Verify the receiver technology and operator generation before assuming that any 318MHz gate receiver can learn the keypad.
Hard-Wired Applications
Current FM137 instructions provide an OUT and COM connection for direct low-voltage activation of compatible gate operator control inputs. A typical compatible operator uses a CYCLE or similar activation input together with COMMON.
Never connect the keypad to an unknown terminal based only on wire color or physical location. Use the gate operator wiring diagram and confirm that the input is intended for a normally open access-control activation device.
Similar Parts That Are Not Automatically Interchangeable
- Linear F310 - professional LinearPro/GTO keypad designation associated with this product family
- Mighty Mule FM137 - Mighty Mule 25-code digital keypad designation
- Mighty Mule MMK200 - newer keypad used for certain newer Mighty Mule applications
- GTO F320 - different keypad model and should not automatically be substituted
- Linear access-control keypads with relay outputs and higher user capacities - different product family
- Garage door wireless keypads using MegaCode or other Linear radio formats - not automatically compatible
Also Known As / Related Part Numbers
- F310
- GTO F310
- Linear F310
- LinearPro F310
- GTO/PRO F310
- FM137
- Mighty Mule FM137
- GTO Digital Keypad
These references are commonly associated with this keypad family. Production date and operator generation should still be checked when replacing an existing unit.
Package Contents
- Digital keypad assembly
- Keypad mounting enclosure / cover
- Basic mounting hardware as supplied with the keypad
Three AA batteries are required and are not normally included. Low-voltage direct-burial wiring, mounting posts, external receivers, and other gate accessories are not automatically included unless specifically stated in the product package.
Technician Note
If a keypad works when hard-wired but not wirelessly, do not immediately replace the keypad. Check receiver compatibility, transmitter programming, receiver antenna condition, installation distance, interference, and battery condition first.
If an existing older keypad is being replaced, identify whether the gate currently uses the keypad wirelessly or through OUT/COM wiring. That distinction can change which replacement keypad or receiver is appropriate.
Before Ordering Checklist
- Confirm whether the existing keypad is marked F310, FM137, or another model.
- Record the exact gate operator model number.
- Determine whether the keypad will be used wired or wireless.
- For wireless use, confirm compatible 318MHz receiver technology.
- Check whether the existing operator uses DIP-switch or learn-button programming.
- For wired use, confirm a compatible CYCLE, OPEN, or access-control activation input.
- Verify whether the operator generation requires a newer keypad such as MMK200 instead.
- Confirm that 25 four-digit user codes meet the site's access-control requirements.
- Confirm that batteries, wire, mounting post, and receiver are included or purchased separately as required.
Installation and Safety Notes
Mount the keypad where a user cannot reach through, around, or over the gate to activate it while contacting the moving gate. The keypad should not be installed inside an entrapment zone or where activation requires a person to stand in the gate's path.
Do not bypass photo eyes, safety edges, obstruction sensing, emergency access, or other required entrapment-protection devices when installing an access-control keypad. If the operator wiring or control input is unclear, have the installation completed by a qualified gate or access-control technician.
Product Questions & Answers
Is Linear F310 the same as Mighty Mule FM137?
The F310 and FM137 are closely related 25-code wired/wireless keypad models and are commonly cross-referenced within the GTO, LinearPro, and Mighty Mule product family. Because production generations differ, verify the existing keypad, operator, receiver, and wiring before treating them as a direct replacement in every application.
How many access codes can the F310 / FM137 store?
The keypad can store up to 25 four-digit entry codes, including codes assigned to individual users. Temporary entry codes can also be programmed for short-term access.
Does the FM137 operate at 318MHz?
Yes. Current FM137 documentation identifies a 318MHz transmitter for wireless operation. The receiver must still be compatible with the keypad's radio system and programming method.
Can the F310 / FM137 be hard-wired instead of used wirelessly?
Yes. Compatible installations can use the keypad's OUT and COM connection to an appropriate gate operator activation input. Verify the operator wiring diagram before connecting the keypad.
Will the FM137 work with MM371, MM372, MM571, and MM572 gate openers?
Current FM137 installation documentation includes wireless programming procedures for MM371, MM372, MM571, and MM572 operators. Verify the exact operator and control-board generation before ordering because compatibility information can differ between older keypad revisions.
What batteries does the F310 / FM137 keypad use?
The keypad requires three AA batteries. Batteries are normally not included, so confirm package contents before installation.
Can I use an FM137 with any 318MHz gate receiver?
No. A matching frequency alone does not guarantee compatibility. Verify the receiver type, radio coding method, operator model, and programming procedure before ordering for wireless use.
What should I check before replacing an older F310 or FM137 keypad?
Check the keypad model, operator model, control-board generation, receiver type, 318MHz compatibility, DIP-switch or learn-button programming method, existing wiring, and whether the keypad is being used wired or wireless.
