This back-up battery keeps your Humane Contain model TX-1 Transmitter Base Station (Included with models HC-8000 and X-10 Electronic Fence systems) operating when the power goes out. It works with the transmitter's built-in automatic recharging circuitry. In the event of a power outage the battery takes over, keeping your dog safely contained for up to 2 days. When power is restored the transmitter automatically recharges the battery. No need to worry about your pooch escaping during power failures. No need to bother changing or recharging batteries. This is a must have accessory for your Humane Contain HC-8000 or X-10 Electronic Dog Fence.