Orban’s 4000 Transmission Limiter protects transmission links, such as digital links, land lines, microwave links, and satellite links, from overload. To achieve simple, error-free setup and operation, the 4000 Transmission Limiter is equipped with the minimum number of controls and indicators necessary to do its job properly. The 4000 Transmission Limiter provides the following features and functions: • transparently protects transmission links (such as digital PCM, NICAM, analog microwave, and telephone/post lines) from overload. Orban’s OPTIMOD-AM, OPTIMOD-FM, OPTIMOD-TV, and OPTIMOD-HF protect broadcast transmitters more effectively. These OPTIMOD units should always be used wherever transmitter protection is required, except for applications requiring “purist” total transparency of sound, without the benefit of OPTI-MOD’s level and loudness control. • can be purchased in single-channel and dual-channel configurations. The dualchannel unit can be strapped for stereo. • accurately and transparently limits levels without producing audible artifacts. • has very low static and dynamic distortion, thus producing extremely transparent, natural audio quality, both below and above threshold. • includes pre-emphasis limiting for five different pre-emphasis curves: 25(j.s, 50jas, 75|J.s, 150|xs and CCITT J.17. • rigorously limits its output bandwidth to 15kHz while constraining overshoots at its output to approximately 1dB maximum. • contains a built-in 100% modulation tone generator, facilitating quick and accurate level setting in any system. • is fully remote-controllable so that large facilities can perform routine network line-up checks centrally. • accurately indicates limiting with a 10-element LED bargraph array. • has a hard-wire relay bypass that can be activated locally or by remote control, and which activates automatically when the 4000 loses mains power. • has a transformerless, balanced 10kH instrumentation-amplifier input and a transformerless, balanced, floating 30Q output to ensure highest transparency and accurate pulse response. (Optional high quality input and output transformers are available to protect against the very high common-mode voltages present on certain long lines.) • is designed to meet all applicable international safety standards.