NLT amplifier
An NLT amplifier ( NLTVr ) was used in the former analog telephone network of the Deutsche Bundespost in order to reduce the attenuation of two-wire telephone lines that were too long if necessary . This was particularly necessary for "external extensions " of telephone systems, as this sometimes caused the planning maximum attenuation of the attenuation plan to be exceeded. So that the specifications of the attenuation plan could be adhered to, it was therefore sometimes necessary to de-attenuate lines with an NLT amplifier.
term
NLT stands for negative line with transistors . or seldom local line amplifiers with transistors .
Mode of action
The mode of operation of the NLT amplifier was fundamentally different from that of conventional amplifiers . It was based on the fact that a network of “ negative resistances ” was switched into the line and reduced or eliminated the attenuation. The NLT amplifier had the advantage over the "classic" amplifiers that it was permeable to alternating current , direct current , dialing characters (e.g. pulse dialing , multi-frequency dialing , diode-earth method ) and charge pulses in both communication directions.
Technical specifications
- Transmission ranges:
- permeable: 0 - 300 Hz
- with amplification and equalization: 300 Hz - 3400 Hz
- permeable: 3400 Hz - 16 kHz
- DC loop resistance : 80 Ω
- Setting options for
- Gain at 800 Hz (adjustable in 11 steps): 2 dB - 6 dB
- Equalization up to 12 dB cable attenuation (adjustable in 11 steps)
- Conductor diameter of the connected line: 0.4 mm (paper or plastic insulated), 0.6 mm, 0.8 mm, 0.9 mm
Installation
The best efficiency could be achieved if the NLT amplifier was operated in the middle of the line. Since this was mostly not feasible due to the given structure of the line network and the frequent lack of a suitable power supply, the NLT amplifiers were usually installed in the exchange or at the customer's.
history
NLT amplifiers were introduced in 1956 and converted to a unitary design in 1976, which enabled them to be installed in the rows of frames of the switching centers or in a wall housing.
literature
- Uwe Horn (Hrsg.): Analog transmission technology with techniques for operational processing. 3rd edition, R. v. Decker's, Heidelberg 1984, ISBN 3-7685-0183-3 .
- Karl Bergmann: Textbook of telecommunications technology. 5th edition, Schiele & Schön, Berlin 1986, ISBN 3-7949-0405-2 .
- Instruction sheets of the Deutsche Bundespost
- Issues 11 + 12/1957 : Negative resistances for de-attenuating uncoiled lines - NLT amplifier
- Issue 1/1977: The new NLT amplifier for uncoiled circuits in the 7 R design
Web links
Individual evidence
- ↑ a b c Handbook of Telecommunications Technology: Basics of Telecommunications Technology. Book series BFt Volume G, 1970, p. 74
- ^ A b c Karl Bergmann: Textbook of telecommunications technology. 5th edition, p. 373
- ↑ a b c Uwe Horn: Analog transmission technology postal guide. 3rd edition, RvDecker's Verlag, p. 72