Quick Reference & Compatibility Guide for the

apt-X™ / 128 System (the DRT128)
 
 
 

I. Installation
Available
 
  II. Operating the DRT128


A.) General Configuration Issues
Like all ISDN gear, the DRT128 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 DRT128, then most likely we've taken care of this for you and you're ready to plug and play. This process is discussed further in section I (C7).



B.) Menu Navigation
The "E" key has two functions: it brings you down into the next level of the menu tree, and, in any given root level, it invokes the parameter setting displayed to the screen. The "*" key brings you up to the next higher level of the menu tree. Repeatedly hitting this key will get you from wherever in the menu you are to the main "Available" screen. The arrow keys will move you horizontally within any level of the menu tree. Within any root level you can scroll through all the possible settings using these keys. If you don't hit "E," the "*" function will move you up a level without changing the current setting. At the main screen, the arrow keys will move you vertically from B1 and B2.



C.) Menu Settings
Each item in the main level of the menu tree displays "Setup Options:" above it. The only branch that has an extra level is "Configure TA."

1.) Audio Mode
Allows you to choose either "Mono" or "Stereo." Because in stereo mode the DRT128 is only capable of a 20Hz-7kHz frequency response, the stereo setting is virtually never used. In Mono mode, the unit's top end extends to 15kHz.


2.) Inverse Mux Mode
Must be set to "Enabled" for normal operation, allowing for the two individual ISDN bearer channels (B-channels) to be aggregated into a single data stream. When "Disabled," the unit can communicate in "clear channel" mode to another apt-X codec at 7.5kHz mono with one call.


3.) APT-X Autosync
Must be set to "Disabled" for normal operation. Used only in conjunction with clear channel mode, it is automatically set to "Enabled" if the "Inverse Mux Mode" is disabled.


4.) Auxiliary Data
The DRT128's aux data channel can essentially serve as a modem connection between two units. Unless you have a special application for this feature, "Auxiliary Data" should be set to "Disabled."


5.) Aux. Data Setup
Not relevant unless the "Auxiliary Data" parameter is enabled, in which instance the data rate should be set to match your application.


6.) Audio Loopback
Must be "Disabled" for normal operation. When "Enabled," the unit sends signal through the encode / decode process, outputting the decoded signal out the appropriate XLR outputs. Note that in mono mode you must use the left XLR input, and the unit will output the decoded signal out both output channels.


7.) Configure TA
Hit the "E" key to descend into this menu level, where you'll find the following five possible branches.

(Tip: Whenever changing the speed dials, SPIDs, or network type you must reboot [power cycle] the unit afterwords in order to communicate the settings to your local telco's end office.)

a.) Set Speed Dial
There are five speed dial positions. Strange as it may sound, operating the unit with North American ISDN requires that your directory numbers (the seven digit phone numbers associated with the two B-channels) be stored in position 4 and 5. In other words, B1's seven digit number should appear in Speed Dial 4, while B2's seven digit number should appear in Speed Dial 5. Note that this effectively leaves Speed Dials 1 & 2 as the only places to store numbers for a 15kHz mono session.
b.) Set ISDN Rate
The two valid North American ISDN line speeds are 56kbits/sec and 64kbits/sec per B-channel. The most important aspect of this setting is that it must match that of the codec you're connecting to.

(Tip: You'll only get the full frequency extension displayed to the screen at 64K. At 56K, roll-off will start just above 13kHz. The midrange, however, won't be effected.)
c.) Set Inband Funct
Must be set to "Disabled."
d.) Set Network Type
This setting must correspond to the switch protocol as provided by your local telco.

(Tip: A bug in the software will sometimes cause the display to default to "NT DMS100" when addressing this parameter, despite it being previously set to something else. This should not be a cause for concern.)
e.) Set Spid
Each B-channel of your ISDN line is assigned a distinct SPID number. The exception is AT&T 5E6 switch protocol, which does not require SPIDs. To change either SPID, first display it to the screen, then press "E" to wipe it clean, then enter the new number and press "E" again to store it.

(Tip: If the network type is set to AT&T 5E6, the DRT128 won't accept SPID entries.)

    D.) Connectors / Controls

1.) Connectors (rear panel)
Line level audio is delivered via the left XLR input (for mono sessions, that is). Audio from the far end is output the XLR outputs. In mono mode, the identical signal is output both left and right. Microphone and headphones are input via 1/4" jacks. Take care to plug the appropriate device into the appropriate jack, as they look the same and are quite close! A 9-pin female data connector is supplied for auxiliary data, and an RJ-45 jack is supplied for connecting the ISDN circuit (post NT1).


2.) Controls (front panel)
The DRT128 has only two physical controls beyond the keypad: mic level gain, and headphone level gain. The "normal" condition for these front panel knobs is the 12 o'clock position. Turn them clockwise to increase the microphone gain and / or headphone gain. If the mic gain is too hot, the red "CLIP" LED will illuminate.   (Tip: EDnet recommends that you DO NOT use the DRT128's internal microphone circuit, but rather that you use an external mic pre-amp and send a line level microphone signal into the left XLR input connector. Nevertheless, the internal mic circuit can be useful in situations demanding maximum portability.)

 E.) Dialing While at the main "Available" screen, position the cursor on the B-channel you wish to dial from. Hit the "D" key, enter the number, then hit "E." After the call completes, you'll most likely see "7K M I" on the screen, indicating that you have a mono connection at 20Hz-7kHz (the "M" = mono and the "I" = inverse mux mode). Then use the arrow keys to move to the other B-channel. Hit "D," enter the second number, and hit "E." After this call connects, you'll likely see "15k M I," indicating that a 20Hz-15kHz mono connect has been established. When you're ready to hang up, the "D" key becomes a disconnect function. Position the cursor on the B-channel you wish to drop, hit "D," and the unit will ask if you're sure you want to drop the call. Hit "E" and the call will disappear. To disconnect a second call, position the cursor at the other B-channel, hitting "D" then "E." Note that both calls must be dropped separately, as described.
 


 
  III. Compatibility To Other Codecs
A.) Compatibility to other apt-X codecs
1.) DSM-100 with Pro-Link ISDN Manager
This is the big brother of the DRT128. It utilizes up to three ISDN lines to achieve a full range (20Hz-20kHz) stereo connection, and "one and a half" ISDN lines (3 B-channels) to achieve a full range mono connection. Of course, when connected to a DRT128 only up to 15kHz extension is possible, in which scenario you are fully compatible.

(Tip: The audio mode [i.e., mono or stereo] of the Pro-Link will override that of the DRT128. Therefore, if you connect to a Pro-Link system and the second call results in a display of "7K S I" then the Pro-Link user is erroneously configured for stereo.)


2.) DSM-100 IMUX
APT manufactures two versions of the DSM-100, one in which the IMUX function is driven within the DSM-100. These units require external terminal adapters (the dialing device) not manufactured by APT. Nevertheless, you should be fully compatible with these sites at up to 15kHz mono.


3.) 3D2
Per a former reseller agreement between APT and Keystone, some APT codecs are marked "3D2," and you'll occasionally hear people refer to their APT systems as "my 3D2." These systems are compatible with yours. A common source of confusion stems from the order of the dial-up numbers at 3D2 sites. Where as with the DRT128 the order in which the numbers are dialed should be insignificant, 3D2 sites require more careful attention to the dialing sequence. If, when connecting to a 3D2 site, you have difficulty establishing a 15kHz mono connection, then you may not be dialing the numbers in proper sequence.

 B.) Non-APT Codecs The apt-X 100 coding algorithm is proprietary to APT. Although Comrex implements a version of this algorithm on some of its products, these codecs are still not compatible with your system. If you need to connect to an MPEG device (e.g., Telos and CCS Musicam), a Dolby codec (AC-2 / AC-3 algorithms), or a G.722 unit (e.g., Comrex) then you'll need to arrange use of our EDLink™ bridging service. Call the 800 number that appears below.

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