Back-up Battery for your HUMANE CONTAIN TX-2 Transmitter Base Station. The TX-2 is the transmitter included with your HC-8000 and X-10 Ultra-fence. This is a rechargeable battery that works with the TX-2's automatic recharging circuitry. In the event of a power outage the battery takes over, keeping your dog contained for up to 2 days. When power is restored the TX-2 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 Ultra-Fence.