Typically, a jammed up B506 or B856 Series timer has experienced a spike in voltage or other damage to the unit resulting in the chip to scrambling. In this event, try pressing the 1 and 4 simultaneously along with power up. The unit will go thru a hard re-boot. When this is complete, press all of the keys and it will finish the process. Then, re-power the unit. If the issue persists, we recommend replacing the unit and protecting the voltage line to the timer for the future.
The battery in the Eagle Signal CX Series timer is soldered in and designed to NOT be replaced. However, the RAYOVAC BR2325T3V or PANASONIC BR2325-1VG batteries are commonly used once the timer warranty has ended.