How to Install Intercoms for Gates

If you're wanting to buy an intercom for your gate whether wireless or wired see the 'Products' menu above. 

Common Problems to avoid

I have been installing and repairing gate intercoms for many years and the most common problems found are weather or insects getting in and wiring that isn't suitable for use outdoors and in the ground, which is a major problem because the only solution is to this is to replace the wiring completely. So its a good idea to make sure the Outside Station is sealed for bugs and weather and you use the correct cabling between the Outdoor Station and building or better still use a wireless intercom although these do still need power at each end.

Installing Wiring for Intercoms 

Wiring for intercoms is low voltage so you don't need to be a registered electrician to install it, although you do need to use the correct type and size of cable so the intercom will work properly and so the wiring doesn't deteriorate in the ground after a few years.

Some Intercoms require only two wires for everything because the electric lock is connected to the outside station, where as others require 4 wires or more if the electric lock is connected to the Handset.  All intercoms listed on this website have diagrams showing what cabling is required, click the "more info" button for this and more.

... how to Install Low Voltage Cable 

Rain Shields

Most outdoor stations for Intercoms are rated as weather resistant and if they are exposed to full rain and sun they may not stand up to it so its a good idea to add a rain shield to the outdoor station or carefully seal around it with clear silicon to prevent water running down the back of it.  Some intercoms come with a rain shield others have them as an optional extra.  

Powering an Intercom System 

Wired Intercoms generally require power connected to the Inside Station only generally from a plug in transformer or plug pack, which can have a low voltage cable added to it so it can be installed away from the Inside Station to keep it looking nice without a power point right next to it.  Some have a power lead so must have a power point next to them. 

However some Intercoms are powered from the outside station. Wireless Intercoms and larger scale wired systems generally require power at both ends or for every station.

wiring diagrams for power to an intercom

Connecting to a Gate Lock or Motor 

Some Intercoms have a lock output that provides either 12VAC/DC OR 18VDC power to release (unlock) an Electric Strike Lock for a Pedestrian Gate or front door whereas others have no voltage output just a clean contact closure (like the press of a button) ideal for directly activating an automatic driveway gate. 

wiring diagram for connecting and electric lock or gate motor

How can you tell what output your Intercom has?  Well apart from reading the instructions if there are three terminals marked "C", "NO" and "NC" then this is a no voltage output with clean contacts.  These sometimes only have the "C" and "NO".  The "C" is a common, "NO" is Normally open and "NC" is Normally closed.  Normally there will be a connection made between the "C" and "NC" terminals and when the "Lock" button is pressed on the indoor station this connection is broken and a new connection is made between "C" and "NO" terminals.  

If the output only has the picture of a lock or a "+" and "-" then this is a powered output.  If you connect a 12VDC lock to it and it buzzes then the output is AC and if it gets a little too warm then its possibly an 18VDC output or higher.  

Matching AC or DC Locks to an Intercoms output 

An Intercom with a 12VDC output can be used with an AC lock but the lock may over heat if powered up for too long so should have a drop down resistor added to minimize this.  The drop down resistor should be at least 5 Watts and a resistance or 5.6Ohms. The same goes for a 12VDC lock powered by an Intercom with an 18VDC output, this too may over heat if powered up for too long so the same value drop down resister should be used.  If an intercom with an 18VDC is used with a 12VAC lock then a drop down resistor or 6.8Ohm should be used.  

An Intercom with a 12VAC output can be used with a DC lock but requires a rectifier or AC to DC converter to work properly.  Even with a Rectifier a DC lock may still buzz if you'd rather it was silent you could add an Electrolytic Capacity across the DC side rated at 100uF or more depending on how quiet you want it. Make sure it is at least 16V and the positive goes to positive.  

Converting an Intercoms Output 

Another way to release an electric lock with a different voltage from an Intercom is to use a relay that matches the Intercom to switch power from a separate power source to the lock. This may be a plug in transformer or power output from a Gate Motor.  The advantage of this is you can use what ever voltage lock you want so long as you have a suitable power supply to match.  The Power supply must have a high enough power rating for the electric lock other wise it may burn out or the lock may not work reliably. 

If the Intercom has a Clean Contact Output and you want to power an Electric lock you can but you also need a separate power source for the Electric Lock.  


If you want to use an Intercom with a powered lock output to open an automatic gate you can but you need to add a relay first that is activated from the voltage output and provides the clean contacts needed to open the automatic gate.  Do NOT connect the powered output of the Intercom to the input of the gate motor control board as you could damage it.  The relay must match the voltage from the Intercom although you can use a Bridge Rectifier and Capacitor as we did above to convert 12VAC to 12VDC and use a 12VDC relay, which are a lot more common than 12VAC relays. 

Connecting a Magnetic Lock 

A magnetic lock requires power applied to it to lock and removed to unlock so is the opposite way around to an electric strike lock.  If an Intercom lock output has three terminals marked "C", "NO" and "NC" then this is ideal for connecting a magnetic lock although a separate power source is required. The power source must have a high enough continuous power rating for the Magnetic Lock otherwise it may not be able to provide enough power to lock the gate properly or worse still burn out and stop working altogether.  The "C" terminal is a common, "NO" is Normally open and "NC" is Normally closed.  Normally there will be a contact made or closed between the "C" and "NC" terminals and when the "Lock" button on the inside station is pressed this contact is broken or opened so will remove power from the magnetic lock. 

If the Lock Output of an Intercom is 12VAC, 12VDC or 18VDC you can still connect a Magnetic Lock but you will need a relay to match with a normally closed (NC) output and a separate power source to match the Magnetic Lock.  12AC relays are more difficult to find than 12VDC relays so you can use a rectifier and capacitor to convert the 12VAC into 12VDC like we did with an electric strike lock earlier.  A 12VDC relay can handle 18VDC for short periods although a drop down resistor is a good idea so the relay doesn't over heat like we did with electric strike locks earlier.  A 1Watt 220Ohm drop down resistor is recommended or a 39Ohm if using an automotive relay.

wiring diagram of how to connect and electric lock

Connecting a Digital Keypad 

A Digital Keypad is normally powered from the same source as the Intercom or Lock as they can accept 12V to 24V AC or DC.  Digital Keypads have clean contact outputs so connecting an Electric Strike Lock, Magnetic Lock or Gate motor is the same as connecting to an Intercom with this type of output.  Digital keypads normally have an input for an external press button, which can also be used for an intercom to activate the keypads output so both the intercom and digital keypad can release a gate lock or open an automatic gate.

wiring diagram of how to connect a digital keypad to an intercom