Two independent receiver ports on the Puma 4000E series allow it to monitor both directions of an in-service E1 line. The activity in each time slot is detected and displayed on the Puma's graphic display. Channels that contain an idle pattern, bit error rate test (BERT) patterns, framing, signaling, or that are "in-use" are identified. Any channel can be highlighted using the Puma's up/down, left/right arrow keys. Users can then easily display more detail about the information in that channel (such as framing), or jump to a BER test. In addition, the Puma's built-in PCM coder/decoder and speaker can be used to listen to speech activity on the selected channel.

The "E1 Monitor" function of the Puma 4000E series is very useful for locating time slots that contain BER patterns. Often, Digital Cross-connect Systems (DCS) and add-drop multiplexors (ADMs)move the channel assignments  around network locations. Because the Puma 4000E series' E1 monitor function does not take the customers' circuit out of service, it is an excellent first step to investigate a trouble report before initiating a customer visit.