IBM 37xx is IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

's family of SNA

Systems Network Architecture

Systems Network Architecture is IBM's proprietary networking architecture created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes the protocol and is, in itself, not actually a program...

 communications controllers used mainly in mainframe environments

Mainframe computer

Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...

.

The IBM 3705 was the oldest of the family. The IBM 3725 was a large-scale node and front end processor

Front end processor

A front end processor , or a communications processor, is a small-sized computer which interfaces to the host computer a number of networks, such as SNA, or a number of peripheral devices, such as terminals, disk units, printers and tape units. Data is transferred between the host computer and the...

, and the IBM 3720

IBM 3720

The IBM 3720 was a communications controller made by IBM, suitable for use in an IBM System/390. Official service support was withdrawn in 1999 in favour of the IBM 3745. The IBM 3720 is unrelated to the similarly-numbered IBM 3270 display terminal system.-External links:*...

 was a remote node that functioned as a concentrator

Concentrator

In telecommunication, the term concentrator has the following meanings:# In data transmission, a functional unit that permits a common path to handle more data sources than there are channels currently available within the path...

 and router. IBM does not support 3705, 3720, 3725 starting from 1999.

These machines are followed by the IBM 3745

IBM 3745

The IBM 3745 is the latest and last of a 37xx family of communications controllers for the IBM mainframe environment. As of mid-2009 there were an estimated 7,000+ of the larger 3745 models still in active production status, down from 20,000 or more in 2007...

, which provides up to eight T1

Digital Signal 1

Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...

circuits. It is no longer marketed, but still supported and used.