The 16SLIU Card connects 16 analog extensions which are typically used for single line telephones and fax machines. Just like the 16ESIU Card, the 16SLIU Card has a Mode Switch (for taking the card out of service), a status LED indicating proper card operation, and a port activity LED to indicate traffic on the card.

The 8SLIU Card connects 8 analog extensions which are typically used for single line telephones and fax machines. The 8SLIU Card has a Mode Switch (for taking the card out of service), a status LED indicating proper card operation, and a port activity LED to indicate traffic on the card.

The SLIU Cards provide high-voltage Message Waiting.