When a carton leaves an upstream zone and is conveyed to its next downstream zone, this upstream zone expects positive confirmation of carton arrival from the downstream zone. This communication occurs automatically along the ConveyLinx network. If a new carton arrives at this upstream zone while this upstream zone is waiting for a downstream arrival confirmation, the new carton will accumulate on this upstream zone. If the upstream zone does not receive this confirmation within the Jam Timer interval, the ConveyLinx-Ai Family Modules will produce an Arrival Jam fault. Once an Arrival Jam occurs, the ConveyLinx-Ai Family Modules will automatically hold any new carton at the upstream zone for a pre-determined Auto Clear Time Timer value and then resume normal ZPA function. By default, the Jam Timer and the Auto Clear Timer values are set to 5 seconds for each. This condition will be indicated on the corresponding Sensor LED on the module

Carton 1 has left PE1 and is on its way to PE2 and because PE1 is clear, Carton 2 is entering Zone 1
Carton 1 disappears but the Zone 2 motor continues to run for the Jam Time period (5 sec. by default). During this time Carton 2 arrives at PE1 but Zone 1 stops because Jam Timer is still timing
When the Jam Timer expires, the Sensor LED blinks to indicate an Arrival Jam and keeps blinking for the Auto Clear Time (5 sec. by default). When Auto Clear Time expires, the Arrival Jam is reset and Carton 2 will release if Zone 2 is empty