Back-up Battery for the Humane Contain TX-1 Transmitter Base Station. The TX-1 is the transmitter included with the HC-8000 Ultra-fence. This is a rechargeable battery that works with the TX-1'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-1 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 Super System.