When an automated vehicular gate system is installed on a property in general access applications, there must be a method to allow emergency vehicles (fire, police, ambulance) access to the property without the gate hindering their entry. The access system must allow for entry through the vehicular gate under three different and unique situations:
1. The system is in service and under normal operation.
2. A power failure has occurred and a power inverter is installed or the gate operator is a DC type with built-in battery backup.
3. A power failure has occurred and the power inverter or DC type gate operator has failed (dead or low charged battery).
Situation 1 - Normal Operation
Under normal operation, there are many devices that can be integrated with the vehicular gate system to allow emergency vehicles access to the property. When any of these devices are activated, the vehicular gate(s) is commanded to open and remains open until the device is deactivated. Typically, the emergency vehicle access device will by-pass the primary access control device (telephone entry system for example) and is wired directly to the gate operator open input. Some of these devices are listed below.
- Click-2-Enter. This system consist of a special radio receiver that allows Fire Departments, Police Departments and Ambulance companies to open the access gates by using their two-way radio installed in their trucks / cars.
- Special Keys and Key Switches - With this system, emergency vehicles each have a special access key that that activates an emergency override key switch. These key switches are typically labeled FIRE DEPT. and are installed in a location at the gate that is visible and easily accessible.
- Lock Boxes - Lock boxes are essentially the same as the key switch option in that a special padlock (that only emergency vehicles have a key too) is placed on the lock box to lock it shut. When the padlock is removed (or cut off), the lock box automatically commands the gate to open and will hold the gate open until the lock box is re-closed and locked. Lock boxes are typically labeled FIRE DEPT. and are installed in a location that is easily visible and easily accessible.
- Siren Sensors - These devices detect the "yelp" mode from an emergency vehicles siren. When the yelp is detected, the gate will open.
- Strobe Light Sensors - These devices respond to the flashing strobe light from the emergency vehicle. When the strobe light is sensed, the gate will open.
- Wireless Transmitters - Like garage door openers, wireless transmitters open the gate from a distance of 75 to 100 feet. These transmitters are specially encoded with a code that is unique to emergency vehicles.
Because of the many different devices available, the city building department should be consulted to determine which method of entry is preferred by the local authorities.
Situation 2 - Power Failure with Power Inverter or DC Type Gate Operator
Power inverters provide back-up power by converting DC power stored in batteries to AC power. When primary AC power fails, the inverter circuit automatically activates to provide continuous AC power to the system. In this manner, all components connected to the power inverter, including emergency access devices, remain in normal operation as if the primary AC power was still present. For this reason, power inverters are the best choice to provide back-up power for automated gate systems.
DC type vehicular gate operators use DC motors and circuits to operate the vehicular gate, and most include batteries as a standby power source. They batteries continue to power the gate operator when primary (AC) power is removed. DC type operators typically operate in one or three different modes. 1) When an AC power failure occurs, the system immediately commands the gate to open and remain open, 2) the gate remains closed until an open command is received, at which time the gate opens and then the system shuts down until AC power is restored, or 3) the system remains operational until the batteries reach a point where they can no longer operate the gate system, at which point the gate will remain open or remain closed. It is important to understand that the batteries in the DC type gate operator only function to keep the gate operator operational. They do not power, or keep functional, access control devcies such as card readers, keypads, telephone entry systems, etc. It is important that the system is designed so that emergency vehicle access devcies are also powered from the batteries in the gate operator to keep these devcies operational.
Power inverters and DC type gate operators provide a trickle charge to the batteries during normal operation. It is advisable that maintenance personnel and property managers check these systems on a monthly basis to assure that the batteries are in good condition and have enough power to open the gate. Batteries in these systems are good, on average, for about two years before they will need to be replaced.
Situation 3 - Power Failure and Battery Powered System Failure
This is the "worst case" scenario that must be addressed during the design of the vehicular gate access system. In other words, system designers and installers must assume that at some point in time there will be a primary (AC) power failure and the batteries in the power inverter or DC type gate operator will fail to open the gate because they are either dead or have a low charge insufficient to operate the system. Under these circumstances, the gate operator must assume a FAIL-SAFE mode. Simply stated, the operator "fails" in a safe condition allowing the gate to be manually pushed open without the need for any keys, cranks, or other mechanical devices. This is an essential feature for both emergency and non-emergency vehicles. Obviously, emergency vehicle personnel cannot waste time looking for keys, cranks, or attempting to force the gate open with bolt cutters, the "jaws of life" or other mechanical devices. They also cannot wait for maintenance personnel to arrive to activate gate release mechanisms that are typically located on the inside of the gate. Likewise, apartment and gated communities cannot allow a situation to develop where residents are "locked" out of their homes. Many Fire Department regulations require that "fail-safe" gate operators be installed to allow emergency vehicle access during power outages.
Automatic vehicular gate systems provide convenience and limit traffic in gated communities, apartment complexes, condominiums, and private homes and businesses. When vehicular access is restricted, there must be a means to allow emergency vehicles access in the overall design of the system. This design must include failure modes under the worst-case scenario, and the access system must have in place equipment and products to over come the worst-case situation. DKS can provide you with vehicular gate products that meet these requirements.