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Quick Reference & Compatibility Guide for the
Telos Zephyr
Your EDnet supplied Telos Zephyr is compatible with a number of MPEG Layer II / Layer III as well as G.722 audio codecs, bringing with it a certain degree of complexity in configuration. The purpose of this document is to provide clear, concise instructions for the set up of both your Zephyr and other compatible codecs. As its title implies, this guide is intended as a quick reference tool only; you should refer to the Zephyr's manual for a more comprehensive understanding of the unit's complete functionality.
I. Zephyr Specifics
A.) General Configuration Issues
Like all ISDN gear, the Zephyr's terminal adapter requires configuration specific to the attached line. This includes switch protocol, directory numbers, and SPIDs. If EDnet has provided your telco line as well as your Zephyr, then most likely we've taken care of this for you and you're ready to plug and play.
If you're not using an external NT1 (network terminator device), then the ISDN line should plug into the "U" interface jack on the rear panel (the lower jack). Note that this will require an RJ-11 telco connector, the standard 4-conductor telephone plug. After a few seconds the small green LED next to the telco jack should stabilize and glow solid. Assuming the unit is properly configured vis a vis the attached line, the left side of the rectangular LCD display on the front panel should shortly read 'Ready' in two places, at which point you're set to go!
B.) Menu Navigation
Menu navigation on the Zephyr is accomplished by a combination of 5 keys: 'UTIL', 'SEL?'??'SEL?', 'YES', and 'NO'. UTIL evokes the configuration mode. After hitting this key, one of the three parameters in the main utility window will be bracketed. The SEL??/?SEL??keys scroll through the various parameters. Within any given parameter, the NO key cycles through the possible choices. Hit the YES key to load in the option currently displayed within the brackets. To return to the main menu from anywhere in the system, hit the 'HELP' key twice.
C.) Transmission Modes
Note that on the Zephyr, parameter changes set both the algorithm (e.g. Layer II / Layer III) and the the algo mode (e.g. mono / stereo).
1.) MPEG Layer II
Uses perceptual coding techniques to achieve compression factors of about 6-8:1, dividing the frequency spectrum into 32 bands.
a.) Mono (Zephyr=L2MONO128 or L2MONO)
Full bandwidth in '2-line' mode (which the Zephyr terms 'L2MONO128'), utilizing both ISDN bearer channels (B-channels); half bandwidth in "1-line" mode with a single B-channel ('L2MONO' on the Zephyr).
b.) Dual Mono (Zephyr=L2STEREO)
Two discrete channels, but limited to half bandwidth.
c.) Joint Stereo (Zephyr=L2JSTEREO)
Not totally discrete, but instead economizes on bits by only coding information once that's redundant to both channels. Signal above 3kHz is summed to mono and panned to one of seven discrete positions.
(Tip: Works quite well for stereo material, but may cause artifacts if disparate information is sent to each channel simultaneously.)
2.) MPEG Layer III
Employs the same general perceptual coding scheme as Layer II, but divides each of the 32 frequency bands into 18 sub-bands, for 576 total bands. Achieves compression factors of about 12:1.
(Tip: As the audio range increases, so does the amount of data compression and thus the potential artifacts. If full 20kHz extension is not required, quality will improve utilizing the 32kHz sampling frequency incorporated in Layer III. Where as the top end will be limited to 15kHz there'll be more bits available to code the critical midrange frequencies.)
a.) Mono (Zephyr=L3DUAL)
Achieves full bandwidth using one B-channel. Best quality with 32kHz sample rate and 64k ISDN speed, although bandwidth will be limited to 15kHz.
b.) Joint Stereo (Zephyr=L3JSTEREO)
Not discrete, as in Layer II JStereo. Uses a matrixed L+R / L-R scheme. Provides excellent mono sound quality when feeding the single source equally to both channels.
c.) Stereo (Zephyr=L3STEREO)
Totally discrete, full bandwidth stereo, utilizing one B-channel per audio channel. This mode will facilitate talent and time code moving in the same direction.
(Tip: Discrete stereo should be used in place of JStereo if the material is later to be fed through surround sound systems.)
3.) G.722
An algorithm with extremely short delay time, popular for remote broadcasting feeds. Uses one B-channel and accords 7.5kHz to the top end. If a site has a Comrex codec, it's probably G.722.
4.) G.711
This is the algorithm POTS (Plain Old Telephone Service) uses. The Zephyr will place a call to regular voice telephone. In order to use this feature, your ISDN line must be provisioned for both data and voice on at least one of the B-channels.
D.) Encoder/Decoder Parameters
1.) "Xmt"
Sets the transmit mode (the encoder). Note that confusion frequently arises regarding Telos' nomenclature. 'L2MONO' refers to CCS 1-line mode, or in other words a half-bandwidth sessions using only one B-channel. 'L2MONO128' refers to a full-bandwidth mono session employing both B-channels (thus the '128', but only if the ISDN line speed is set at 64k; otherwise you'll literally be at '112').
2.) "Rcv"
Sets the receive mode (the decoder). You'll notice that fewer choices appear here than in the 'Xmt' menu. That's because the encoder does the work as far as the specific algorithm mode. In other words, the decoder, if set to 'L2', will decode any valid Layer II transmission mode it sees.
3.) "Rate"
A two-fold parameter, 'Rate' sets both the ISDN line speed and the sampling frequency. In Layer II, only a 48kHz sample rate is allowed, while Layer III allows 48kHz as well as 32kHz. When using G.722, 32kHz is recommended. Note that the transmit and receive modes operate independently in each direction; assuming each site's decoder is set complimentary to the other site's encoder, both will get a lock.
E.) Dialing
To place a call on the first B-channel, hit the 'DIAL' key, enter the number, and hit DIAL again. If the call connects successfully, the red line 1 LED will illuminate and the call timer ('0:00') will appear in the LCD display window. Hitting the DIAL key again will prompt you to enter the second dial-up number. Enter that number and hit DIAL a fourth time. The line 2 LED should now be on, at which point B2's call timer will appear. If your unit is set to receive a like protocol of that which the remote site is transmitting, the red 'LOCK' indication will illuminate. To disconnect the session, hit the 'DROP' key twice.
II. General Compatibility Issues
A.) Common Issues
Regardless of what kind of codec you're connecting to, there are some common issues that need to be addressed, preferably prior to the session. These include:
1.) ISDN Rate
Both sides must be set to place / receive calls at the same line speed, be it 56 or 64k. A nice feature on the Zephyr is that it will automatically set its line speed to match the incoming call. This makes rate mismatches far less common. But don't forget, if the Zephyr is placing outbound calls to another type of codec you can't rely on this automation.
2.) Algorithm
Will the session employ MPEG (Layer II or III), G.722, etc.?
3.) Algorithm mode
Does the session require mono, stereo, etc.?
4.) Independent/Dependent
Although the Zephyr doesn't have an independent vs. dependent setting per se, this is a concept you'll need to be aware of when connecting to a site with a Musicam codec. Essentially, the Zephyr is in 'independent' by default, while the Musicam codec must overtly be put there (see Section 3 of this document).
B.) Time Code
For Layer II operation, EDnet recommends that the SMPTE be generated from the same end that's recording. This end transmits in 'Dual Mono' mode, sending time code down one channel and talk-back down the other. The remote end sends full bandwidth audio back the other way. An offset can be built by measuring the round trip SMPTE delay. For Layer III operation, SMPTE and talent can go in the same direction using the discrete stereo mode. In this scenario, however, the talent will only be coded on one B-channel, and as a result of the high degree of compression the quality may suffer.
III. Compatibility With Other Codecs
A.) CCS CDQ2000
This codec does MPEG Layer II only. All four "line select" switches must be in the down position, and the large silver knob should be at either 112 or 128, depending on whether the Zephyr's Rate is set to 56 or 64k. On the rear panel of the CDQ2000 there are two rows of dip switches. On bottom row, dip switch #6 must be in the UP position for compatibility with the Zephyr. This is equivalent to independent = yes on the CDQPrima.
(Tip: Xmt = L2MONO128 [for mono] or L2JStereo [for stereo] / Rcv = L2)
B.) CCS CDQ1000
This is a 'one line' device, employing a single B-channel at either 56 or 64k and yielding between approximately 8 and 10kHz of top end. The best frequency response is obtained using a 64k ISDN line speed. The CDQ1000 should be in MPEG mode with a 48kHz sample rate and a ISDN rate matching that of the Zephyr.
(Tip: Xmt = L2MONO / Rcv = L2)
C.) CCS CDQPrima
This codec is capable of MPEG Layers II and III as well as G.722. Any Prima running relatively recent software is equipped with a factory supplied set of 'Quick Configurations'. These will configure the unit for a variety of other codecs. For Layer II sessions, numbers 26 and 27 apply to the Zephyr (#26 = 56k line speed; #27 = 64k line speed). Note that both these Quick Configs will set the Prima to transmit in joint stereo. If it's a mono session, the Prima user will need to manually change their encoder's 'Algo Mode' parameter to mono. If these Quick Configs don't work, you'll likely need to contact EDnet's technical support to solve the problem.
(Tip: Regardless of the nature of the session, the 'Independent' parameter on the Prima's decoder must be set to 'yes.')
D.) CCS RoadRunner
This is the "little brother" of the Prima series and is a mono only codec, capable of MPEG Layers II and III as well as G.722. Like the Prima, the RoadRunner is equipped with a factory supplied set of 'Quick Configurations'. As of this writing EDnet recommends working with RoadRunners in Layer II mode only, and the appropriate Quick Configs are numbers 15 and 19 (#15 = 56k line speed; #19 = 64k line speed). Again, if these Quick Configs don't work, you'll likely need to contact EDnet's technical support to solve the problem.
E.) 'Mono' Zephyr
Some Zephyrs lack the extra DSP card necessary to transmit in '2-line' mode. Unfortunately, this means that the highest quality mono transmit setting (L2MONO128) is unavailable to these sites. In this case, the best quality is generated by working in Layer III Dual Mono with a ISDN line speed of 64k and a sampling rate of 32kHz. Mono Zephyrs can, however, receive in '2-line' mode, either mono or stereo. Telos' terminology refers to this as '3 DSP mono.'
(Tip: To determine if a Zephyr is mono only, attempt to load a 2-line transmission mode into the Xmt parameter [e.g. 'L2MONO128']. If it is a so-called mono unit, it will yield a "no hardware support" message.)
F) Comrex G.722 / CCS Micro 56
These codecs only do G.722, the main advantage being a very short delay time, the disadvantage being a top end limited to about 7.5kHz. In the case of the Micro 56, a 64K line speed is not possible. Most Comrex codecs, using two B-channels, can achieve 15kHz extension but only to another Comrex. Should you desire this added quality, EDnet can bridge you.
(Tip: Xmt = G.722 / Rcv = G.722 / Rate = 56 or 64/32kHz)
G.) Dolby AC-2 / AC-3 / Dolby Fax / APT-X / 3D2
These refer to proprietary coding schemes from Dolby as well as Audio Processing Technologies, both of which are incompatible with Telos. EDnet can bridge you to these sites.
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