This wiki describes work within the Osmocom community to develop E1/T1 hardware interfaces. There were several different approaches taken, implemented to a verying degree and experimented with.If you are a user and not a developer, there are so far only two hardware interface projects that have reached the stage where they can be cnsidered ready/usable:
- E1_tracer - a passive E1 tracer that can record the bi-directional bit-stream of an E1 line
- ICE40 E1 USB interface - an inexpensive, open source hardware, gateware, firmware and software interface for terminating E1 circuits.
E1/T1 TDM technology¶
E1/T1 lines were pretty common in the 1990ies and up until about 2010, as they built the heart of many connections to the digital, circuit-switched telephony (ISDN) network.
Today (2019), E1/T1 are mostly only found in connection with GSM base stations (BTS), where the Abis interface of a BTS is still officially only specified over E1/T1.
Hardware for connecting E1/T1 to a (Linux) computer has always been expensive, and is rather difficult to find. Also, it only comes in PCI and PCIe form-factor, making it unsuitable to many popular embedded Linux platforms (whether ARM or x86) which don't feature such interfaces.
We've been wokring on creating E1-USB adapters based on a variety of approaches, see further wiki pages for details.
- Design + Theory + Background
- E1 tracer
- Linux generic HDLC layer + DAHDI
- Proposed efficient TDMoIP