The miniature SRM-5A, SRM-6A and SRM-6L are asynchronous short range modems connecting full duplex, asynchronous terminals to computers. The SRM-5A and SRM-6A operate at data rates of up to 19.2 kbps with a range of 4.5 km (2.8 miles) at 9.6 kbps. The SRM-6L operates at data rates of up to 19.2 kbps up to a range of 3.2 km (2 miles).

The SRM-5A is fully compatible with the SRM-6A and offers the same features in half the size.

The SRM-6L offers the unique feature of insensitivity to wire polarity: There is no need to observe + and-connections when using twisted pairs, making it easy to install and maintain.