MUSICAM USA Frequently Asked Questions

ISDN


Q:        What is ISDN?
A:         ISDN is an all digital switched telephone network provided by the telephone company. Each ISDN line has three channels: two 64 kb/s 'B', or bearer, channels, and one 16 kb/s 'D', or delta channel. The two 'B' channels are for user data, and can be used independently from each other as two separate data channels. The phone company uses the 'D' channel for signaling, such as call setup and termination, billing and configuration. Unlike regular telephone service where the customer equipment and line is analog, ISDN is truly end-to-end digital service.

Q:         What are terminal adapters and what is an NT1?
A:         An ISDN terminal adapter is similar in function to a telephone modem. Call setup (dialing), rate negotiation, and call termination functions are all performed by the terminal adapter. In addition, the terminal adapter converts the user data into a format required by the network for transmission.

The NT1 is an interface converter. The three channels of ISDN are all combined onto a single twisted pair from the service provider. The terminal adapter requires that the three channels be separated into a 4-wire system, and that is the function of the NT1. In North America, the phone company provides a 2-wire 'U' interface and an NT1 is required. It is the user's responsibility to provide the NT1. Elsewhere, the phone company provides the NT1. Some terminal adapters sold in North America integrate the NT1 functions into the terminal adapter, such as our TA301 internal terminal adapter and the ADTRAN 2X64 terminal adapter.

Q:         How much does ISDN cost?
A:         This question is a little hard to answer. The cost of ISDN varies significantly, depending on distance from central office, popularity of ISDN in the area and other factors. The monthly and per-minute charge (per line) should be comparable to standard phone service in the U.S., but remember that a standard ISDN BRI is two lines. Your service provider may not offer unlimited usage local ISDN service. Installation costs range from free to several hundred dollars.

Q:         How do I order ISDN?
A:         Most phone companies have special numbers to call for ordering ISDN. For a list of numbers,
CLICK HERE , or contact us. When ordering ISDN, make sure to specify that you want long-distance service on both 'B' channels, and specify a long distance carrier.

Q:         How do I provision my ISDN service for use with audio codecs?
A:         ISDN provisioning, especially in North America, can be very confusing. You need to specify parameters such as voice and/or data use, number of terminals, terminal type, and many other parameters. If your service provider asks for or understands the meanings of 'Capability Codes', ask for Capability Code 'R' (formerly known as Generic Data I). If they do not understand these codes,
print these pages and FAX them to your service provider. When ordering ISDN, make sure to specify that you want long distance service on both 'B' channels, and specify a long distance carrier.

Q:         Why did the phone company give me two phone numbers?
             Must I use them both?

A:         Users of ISDN have access to two individual 64 kb/s bearer channels. These channels can be used separately or together. Most areas of North America and some other countries will differentiate these two channels by assigning different phone numbers to each.

Q:         The phone company only gave me one phone number. Do I still have 2 'B' channels?
A:         Yes. Some areas use only one number for both channels. Callers dial the same number twice for 2-line connections.

Q:         What is a SPID number and do I need to use it?
A:         A Service Profile ID number is an identification tag used by the central office switch in addressing and handshaking to your ISDN terminal adapter. SPID numbers are used in North America only. If your service provider gives you a SPID number or numbers, you must use them for a one-time setup of your terminal adapter. If your system requires SPID numbers and you have entered them incorrectly or not at all, you will not be able to dial, but you may be able to receive calls.

TRANSMISSION MEDIA


Q:         What is the difference between Dedicated Lines, T1 and ISDN?
A:         Dedicated lines are, as the name implies, dedicated connections between two points. Dedicated lines are usually 56 or 64 kb/s, and multiple lines can be combined for higher bit rates. Dedicated lines do not allow dialing into or out of your audio codec.

A T1 is a dedicated line with 1.544 Mb/s capacity, which is based on twenty-four 64 kb/s channels. Since the CDQPrima and many other audio codecs need only a fraction of the 1.5 Mb/s capacity, a maximum of six channels, a whole T1 can be shared between multiple users. This is called "fractional T1." T1 refers to the transport of a DS-1 formatted signal onto a copper, fiber or wireless medium for deploying voice, data or videoconferencing services.

ISDN, Integrated Services Digital Network, is an international standard for switched digital communications. ISDN offers a full range of enhanced services supporting voice, data, and image applications through standard interfaces over a single telephone line. ISDN provides a means of integrating these services and modernizing communication networks to provide information and management efficiency.

ISDN Basic Rate service divides a standard telephone twisted pair into three digital channels capable of simultaneous bi-directional voice and data transmission. The three channels are comprised of two Bearer (B) channels at 64 kb/s and a Delta (D) channel at 16 kb/s, and is also known as 2B+D. ISDN Primary Rate is also available with 23 'B' and one 64 kb/s 'D' channels.

Q:         What is Switched-56?
A:         Switched-56 was the first switched digital service to be offered to the public. Pre-dating ISDN by several years, Switched-56 offers 56 kb/s switched digital connectivity. Although the data is clocked at 64 kb/s, unlike ISDN which has a separate data channel for signaling and billing, Switched-56 used one data bit per 8-bit byte for signaling, yielding 56 kb/s throughput. Although Switched-56 is still available in most areas, it is generally not cost competitive with ISDN.

Q:         Can I connect from ISDN to Switched-56?
A:         Absolutely! Just set your ISDN equipment to recognize or dial at 56 kb/s.


GENERAL


Q:         Will your codecs allow me to send audio over the Internet?
A:         Until recently, the worlds of ISDN and Internet (or IP) connectivity were distinctly separate, with professional codecs unable to communicate in real time via IP. Now, with the amazing new NetStar Codec, it's possible to connect not only via ISDN, but also via IP, and to connect SIMULTANEOUSLY via ISDN and IP. See NetStar for details.

Q:         Why compress?
A:
         Bottom line…Cost! Sending uncompressed audio digitally from one location to another requires 1.5 Mb/s for two channels (stereo). This capacity is just too expensive for most users.

Q:         C'mon! Compressed audio sounds audibly worse than uncompressed, right?
A:
         This depends on the compression ratio and the algorithm used. For stereo, at low bit rates, say, less than 96 kb/s, yes. The audio at these bit rates is bandwidth limited, and may have noticeable artifacts. This is not to say that low bit rates can't be used. There are many applications where bit rates as low as 56 kb/s are perfectly acceptable.

At ISDN bit rates, 112 or 128 kb/s, depending on algorithm, it may take a well trained ear to differentiate between the source and the compressed audio. At higher bit rates, 192 to 384 kb/s, depending on algorithm, it may be impossible to differentiate between the original and the compressed audio, even with sophisticated test equipment.

Q:         Which algorithm is right for me?
A:
         Selecting the right algorithm and bit rate depends mostly on application and desired results. Please see our Tech Tips for a tutorial on selecting the right algorithm.

Q:         What's good about Layer 3?
A:
         Layer 3 excels at delivering high quality monaural audio on a single ISDN 'B' channel, true stereo on two. With 15 kHz bandwidth and nearly inaudible artifacts, Layer 3 delivers near CD quality audio for audition purposes. Bear in mind that Layer 3 does not cascade well and may be adversely affected by audio processing such as companding and equalization.

Q:         Isn't MUSICAM® simply your implementation of ISO/MPEG Layer 2?
A:         Yes, and that's what makes it so good! The ISO/MPEG Layer 2 Standard defines only the bit stream and the decoder functions, leaving the encoder design and implementation to the manufacturer. MUSICAM USA has performed hundreds of tests, spending thousands of hours adjusting and fine-tuning our encoding system. In addition, MUSICAM USA has implemented a dynamic bit allocation function in the encoder that yields noticeable improvements to the MPEG Layer 2 algorithm.

Since the decoder is defined and all improvements are in the encoding, any decoder, regardless of manufacturer, will sound better when connected to a MUSICAM USA codec.

Q:         If FM broadcasting cuts off at 15 kHz, why do I need a codec that gives me 20 kHz performance?
A:
         As with any other 'system', whether mechanical, electronic or audio, the weakest link in the chain should be the last. No matter how good the next stages are, it is impossible to make a poor sounding source sound better than it is. A noisy, limited fidelity source will just sound worse as it passes through other 'links' in the audio chain, therefore the most band-limited and nosiest link should be the last.

Also, we're working toward a DAB (Digital Audio Broadcasting) system in the U.S., and that system will deliver 20 kHz near-CD quality audio. The codec you buy today should be capable of this level of performance.

Q:         Why do I need to be careful about "cascading"?
A:
         Just because you have only one compression cycle in your audio chain doesn't mean that you shouldn't worry about cascading. Most commercial production houses use compression in their product. Increasingly, voice talents usually do not travel to the recording studio for voice-over work; they use ISDN codecs and 'work from home'. Most remotes use compression technologies to deliver the audio to the studio. Indeed, when a commercial, sporting event, news program or live concert is aired, it may have already passed through several compression cycles.

Q:         How does CDQPrima help me to avoid problems with cascading?
A:         CDQPrima gives you cascade protection in two important ways: 1) The higher the bit rate used, the less compression is performed and more compression cycles can be tolerated. For example, at 128 kb/s joint stereo, the limit is about two compression cycles before artifacts become audible. At 384 kb/s, the limit is raised to 15 compression cycles. CDQPrima supports bit rates up to 384 kb/s for MUSICAM enhanced Layer 2 and 320 kb/s for Layer 3. 2) MUSICAM enhanced Layer 2, at any bit rate, cascades better, with fewer artifacts than either unenhanced MPEG Layer 2 or Layer 3.



CDQPrima AND ROADRUNNER


Q:         Which CDQPrima model is right for me?
A:         With five models to choose from, there is a model for every need and budget. Keep in mind that all CDQPrima models have the same superb specifications and deliver the same outstanding audio quality.

The first question to ask is "What size unit do I need, 1 or 2 U high?" The 1 U high models (110 and 120) support only a single digital interface, so multiple ISDN lines or stereo audio distribution applications cannot be supported unless external terminal adapters are used. 1U high models cannot support ISDN rates higher than 128 kb/s using internal terminal adapters, although external terminal adapters can be used for transmission rates up to 384 kb/s. In addition, 1U high models cannot support SMPTE Time Code, optical AES/EBU digital audio I/O, two RS232 ancillary data channels or more than 4 remote contact closures.

Another question to ask is "Will I be expanding the system in the future?" You can buy a basic 200 Series system (a CDQPrima 210, 220 or 230 with a single ISDN terminal adapter or other digital interface), and add additional terminal adapters or digital interface modules, SMPTE Time Code and remote relay inputs/outputs as needed. With 100 Series models expansion is limited.

The next questions to ask is "Do I need the VU meters and headphone output?" If the answer is yes, then Models 120 and 220 are right for you. "Real-time spectrum analysis, phase displays and hot keys?" CDQPrima Model 230 is your choice.

CLICK HERE for a complete list of models and features.

Q:         Why is RoadRunner the ideal product for mono ISDN remotes?
A:         RoadRunner is a complete portable package that comes complete with everything you need for professional quality monaural remotes. RoadRunner contains a three-input audio mixer, a full featured multiple algorithm, multiple bit rate audio codec, and an ISDN terminal adapter with integrated NT1 (where required). Unlike some other portable monaural codecs, the RoadRunner offers a choice of algorithms and bit rates, and was designed from the ground up for monaural operation, not as a stripped-down stereo codec.

Q:         What digital interface module is correct for my transmission medium?
A:         Since ISDN is a switched service, some device is required for dialing, call setup and termination. This is the function of the ISDN terminal adapter. A terminal adapter can be internal to the codec or external.

MUSICAM USA has three models of internal terminal adapters designed for use in all CDQPrima and RoadRunner codecs. All models support one ISDN BRI for a maximum of 128 kb/s. The TA101 and TA201 terminal adapters are both designed for international use. Providing a 4-wire 'S' interface to the network, these models require the use of an external NT1 when used in North America. The TA301 has a built-in NT1 for use in North America only ('U' interface).

External ISDN terminal adapters are available from many manufacturers, and are fully compatible with all MUSICAM USA codecs. When using an external terminal adapter with a CDQPrima or RoadRunner, you will need a digital interface module to interface the terminal adapter to the codec. MUSICAM USA provides two different models that plug into your codec. Digital interface module DIF101 provides an RS422/X.21/RS530 interface and DIF102 provides a V.35 interface. Which one you need depends on model and manufacturer of the terminal adapter.
A CSU/DSU is used with dedicated lines, T1 and E1 systems. Modems are required for Switched-56. Each end of the circuit requires a CSU/DSU or modem. The CDQPrima or RoadRunner requires a digital interface module to connect to the DTE port of the CDU/DSU or modem. Depending on the DTE interface of the CSU/DSU, a DIF101 (RS422/X.21) or DIF102 (V.35) is required.

Q:         Can I use different algorithms in each direction? Why might I want to do this?
A:         Yes. You may want to sent high fidelity stereo to the studio, using MUSICAM enhanced Layer 2 or MPEG Layer 3 to achieve near-CD quality audio, but low fidelity, low delay audio from the studio to your location for cueing and talk-back.

Q:         Can I send my program to multiple destinations?
A:         Yes. Our 200 Series CDQPrima allows you to send the same audio program to as many as 6 locations simultaneously. Our CDQPrima 110 and 120 can send stereo to one location and mono to two. And the RoadRunner can send mono to two locations simultaneously.

Q:         Is it true that you can program my CDQPrima from the factory over the ISDN line?
A:         Yes. CDQPrima's far-end remote control capabilities make it easy for us to troubleshoot your codec and terminal adapter, program your Prima Logic Language macros, update your speed dial directories and reconfigure your codec. What makes this feature so powerful is that you can also program and monitor any CDQPrima that you connect to as well. And our Windows Remote Control program makes far-end remote control even easier!

Q:         Why can't I dial long distance over my ISDN line?
A:         With ISDN, if you don't specify that you want long distance service, you don't have long distance service. When ordering ISDN in North America, you must explicitly request long distance service and specify a long distance carrier for both 'B' channels. In addition, your service provider may terminate your long distance service for no apparent reason. This happens quite often in North America. If you can dial locally, but not long distance, contact your service provider. In most instances, using access codes (MCI = 10222, Sprint = 10333, AT&T = 10288) may work until your provider can be contacted.

Q:         How do I manually dial your 24-hour Music Line?
A:         Our 24-hour Music Line will automatically configure for 56, 64, 112 or 128 kb/s, single or two-line, MPEG Layer 2. The music line will frame to any incoming 2-line calls as long as the second line connects within 5 seconds of the first line. This means that you must use an auto dialer for all 112 and 128 kb/s 2-line calls. If you do not have the capability to auto-dial, you can test only single-line calls. Set your codec to the appropriate bit rate, algorithm and line format. The test number for line 1 is (732) 706-1437 and for line 2, (732) 706-1497.

Q:         I don't have an auto-dialer. Can I test 2-line connections?
A:         Yes, two ways. Configure your codec with the appropriate 2-line settings. From your first line, dial into your second line. You will hear whatever audio you send. Or call your local service provider or MUSICAM USA Tech Support and ask for ISDN loopback numbers in your area.

Q:         Do you have a test line for G.722 or MPEG Layer 3?
A:         No; however, if you contact MUSICAM USA Tech Support, we will be happy to temporarily set one up.

Q:         What does 'NF', 'LF' and 'N-' on the top line of CDQPrima's LCD display mean?
A:         These are instantaneous status indicators. The 'N' means normal, or not in loopback (L) mode. The 'F' means the decoder is framed, the '-' means it is not framed.

Q:         Occasionally, I see one or more 'O' characters flash on my CDQPrima LCD display. What do these mean?
A:         The 'O' stands for Overload. These indicators will flash when either the input audio to the encoder (to the left of the 'NF') or the received audio to the decoder (to the right of the 'NF') is overloaded. If these indicators are present, reduce the appropriate audio level.

Q:         What does a 'B' on the top line of the LCD display indicate?
A:         The 'B' stands for Bit Errors, and it indicates errors in the transmission media. The 'B' may also be accompanied by alarm relay chatter and audio muting.

Q:         My LCD display went blank, but the CDQPrima still works. What happened?
A:         Some models of the CDQPrima may reset to a blank display after a reset of factory defaults. Refer to the troubleshooting section of the CDQPrima Technical Reference Manual for resetting the display.

Q:         Far-end remote control is a very powerful feature, but do I need a computer terminal to control the far-end CDQPrima?
A:         Yes. Far-end remote control works only with a terminal or PC connected to the local CDQPrima. Far-end remote control is not possible from the CDQPrima keypad or from the RoadRunner.

 

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