Zweikanalton
Encyclopedia
Zweikanalton is a television
sound transmission system used in Germany
, Austria
, Switzerland
, and other countries that use or used PAL-B or PAL-G. It relies on two separate FM
carriers
.
This offers a relatively high separation between the channels (compared to a subcarrier
-based multiplexing
system) and can thus be used for bilingual broadcasts as well as stereo
. Unlike the competing NICAM
standard, Zweikanalton is an analog
system.
The second sound carrier also contains a 54.6875 kHz pilot tone to indicate whether the transmission is stereo or bilingual.
The pilot tone is 50% AM modulated with 117.5 Hz for stereo or 274.1 Hz for bilingual.
Zweikanalton can be adapted to any existing analogue television system, and modern PAL or SECAM television receivers generally include a sound detector IC that can decode both Zweikanalton and NICAM.
Zweikanalton can carry either a completely separate audio program, or can be used for stereo sound transmission. In the latter case, the first FM carrier carries (L+R)/2 for compatibility, while the second carrier carries R (not L-R.) After combining the two channels, this method improves the signal-to-noise ratio
by reducing the correlated noise between the channels.
The frequencies are chosen such that they cause minimal interference to the picture. The difference between the two sound carriers is 15.5 times the line frequency (15.5 x 15625Hz = 242187.5 Hz) which, being an odd multiple of half line frequency, reduces the visibility of intermodulation
products between the two carriers. The pilot tone frequency is 3.5 times line frequency (54687.5 Hz). The modulated tone frequency is 117.5 Hz for stereo transmission and 274.1 Hz for bilingual transmission. Absence of this tone is interpreted as a monaural transmission.
standard of TV transmission. In this case the second FM carrier is 14.25 times the line frequency, or about 224 kHz, above the first carrier; pre-emphasis is 75 microseconds; the stereo pilot tone frequency is 149.9 Hz; the bilingual pilot tone frequency is 276 Hz; and the second channel carries L-R (not R).
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
sound transmission system used in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, and other countries that use or used PAL-B or PAL-G. It relies on two separate FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
carriers
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
.
This offers a relatively high separation between the channels (compared to a subcarrier
Subcarrier
A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth...
-based multiplexing
Multiplexing
The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
system) and can thus be used for bilingual broadcasts as well as stereo
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
. Unlike the competing NICAM
NICAM
Near Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
standard, Zweikanalton is an analog
Analog television
Analog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...
system.
How It Works
A 2nd FM sound carrier containing the right channel for stereo is transmitted at a frequency 242 kHz higher than the existing mono FM sound carrier, and channel mixing is used in the receiver to derive the left channel.The second sound carrier also contains a 54.6875 kHz pilot tone to indicate whether the transmission is stereo or bilingual.
The pilot tone is 50% AM modulated with 117.5 Hz for stereo or 274.1 Hz for bilingual.
| mode | existing OIRT 6.5MHz or BG 5.5MHz sound carrier contains: | 2nd OIRT 6.742MHz or BG 5.742MHz carrier contains: | pilot tone in 2nd carrier: |
|---|---|---|---|
| mono | mono | carrier is absent | none |
| stereo | mix of left & right (L+R)/2 | right audio channel | 54.6875 KHz 50% AM with 117.5 Hz |
| bilingual | 1st language | 2nd language | 54.6875 KHz 50% AM with 274.1 Hz |
Zweikanalton can be adapted to any existing analogue television system, and modern PAL or SECAM television receivers generally include a sound detector IC that can decode both Zweikanalton and NICAM.
Zweikanalton can carry either a completely separate audio program, or can be used for stereo sound transmission. In the latter case, the first FM carrier carries (L+R)/2 for compatibility, while the second carrier carries R (not L-R.) After combining the two channels, this method improves the signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
by reducing the correlated noise between the channels.
The frequencies are chosen such that they cause minimal interference to the picture. The difference between the two sound carriers is 15.5 times the line frequency (15.5 x 15625Hz = 242187.5 Hz) which, being an odd multiple of half line frequency, reduces the visibility of intermodulation
Intermodulation
Intermodulation or intermodulation distortion is the amplitude modulation of signals containing two or more different frequencies in a system with nonlinearities...
products between the two carriers. The pilot tone frequency is 3.5 times line frequency (54687.5 Hz). The modulated tone frequency is 117.5 Hz for stereo transmission and 274.1 Hz for bilingual transmission. Absence of this tone is interpreted as a monaural transmission.
System M variant
There is a version of A2 used in Korea, compatible with the System MSystem M
System M, sometimes called 525 line, is the analog broadcast television system used in the United States since July 1, 1941, and also in most of the Americas and Caribbean, South Korea, and Taiwan. In addition, Japan uses System J, which is nearly identical to System M. The systems were given...
standard of TV transmission. In this case the second FM carrier is 14.25 times the line frequency, or about 224 kHz, above the first carrier; pre-emphasis is 75 microseconds; the stereo pilot tone frequency is 149.9 Hz; the bilingual pilot tone frequency is 276 Hz; and the second channel carries L-R (not R).
Other names
Zweikanalton is known by a variety of names worldwide. Most commonly used names are German Stereo, A2 Stereo, West German Stereo and IGR Stereo.Related topics
- Multichannel television soundMultichannel television soundMultichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
(3 additional audio channels in an NTSC-format audio carrier.) - NICAMNICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...