The TAS 240 Voiceband Subscriber Loop Emulator (VSLE) is a general purpose loop emulator for voiceband applications. The VSLE provides simulation of up to four (4) loops in a single enclosure. The VSLE has been designed specifically to provide the loop emulation required for testing high-speed voiceband modems per the specifications provided by (or currently proposed by) the EIA/TIA TR30.3 sub-committee, ETSI, and the CCITT. The VSLE simulates four loops in order to completely emulate the network which interconnects two modems. The four loops are allocated to the following: • One "main" loop between the Telephone Network Emulator station A, and modem "A" • One "main" loop between the Telephone Network Emulator station B, and modem "B" • One "tracking" loop to provide the balance network for the station A hybrid • One "tracking" loop to provide the balance network for the station B hybrid The second pair of loops, "main" loop for station B and its associated tracking loop, is an optional feature of the VSLE. The VSLE also emulates impairments such as noise, impulse hits and mutiple frequency interference, which are present on the local loops. These impairments are specified by the developing TIA PN 3857 test specification. Impairments are an optional feature of the VSLE. In addition to loop simulation and impairments the VSLE simulates metering pulses which are present on the local loops of several European countries, and are specified by the ETSI test specifications. Metering pulses are also an optional feature of the VSLE. The available models and configuration of options for the TAS 240 VSLE are as follows: • 240A VSLE with four loops and metering pulses • 240 VSLE with four loops • 240L VSLE with two loops (Loop A with A tracking loop). • 240M VSLE with metering pulses and no loops • 240I VSLE with four loops and impairments The TAS 240 Voiceband Subscriber Loop Emulator (VSLE) is designed to emulate the local loop conditions specified by the EIA/TIA TR30.3, ETSI, and ITU (CCITT) organizations. In addition the TAS 240 will emulate user defined loops. The TAS 240 emulates up to two sets of loops where each set consists of a "main" loop and its associated "tracking" loop. The main loop is used to emulate the Station A or Station B local loop, while the tracking loop is used primarily as the balance network for balancing the Station A or Station B hybrid. Loop B is independent of Loop A. However, each tracking loop is always identical to its main loop. For test configurations which do not require the balance network to be identical to the loop, the tracking loop may be used as a primary loop. The TAS 240 VSLE my be equipped with the optional impairment generator when initially purchased. This option allows the user to control noise, impulse hits, and multiple frequency interference individually. Each of these impairments can also be turned on simultaneously with any of the other impairment operating. Loop impairments are necessary to meet the testing requirments of the developing TIA PN3857 testing standard. The TAS 240 VSLE may be equipped with the optional metering pulse generator when initially purchased. This option allows the user to program the frequency, level, and cadence of the metering (or billing) pulse signal injected onto the specified main loop. Metering pulses are required to meet the ETSI testing requirements of several European countries. The TAS 240 is intended to be integrated into a complete modem test system under control of TASKIT. The components of the overall test system include a TAS 1022 Gemini Dual Terminal Emulator, and either the TAS 100 Series or TAS Series II Telephone Network Emulator. Alternatively, the TAS 240 may also be used as a standalone product, controlled manually via the front panel, or remotely via RS-232 or IEEE-488.