Telephony Gain Generation (GainGen)
Features
- Generates any decibel level of gain, positive and negative, used in telephony applications
- Provides up to 32 user-programmable gain levels
- Supports both µ-Law and A-Law encoding algorithms
- Provides fully configurable gain control
- MegaWizard® Plug-In features gain setting, editing, and µ-Law to A-Law and/or A-Law to µ-Law conversion
Block Diagram
Figure 1 shows the block diagram for the megafunction.
| Figure 1. Block Diagram |
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Description
The GainGen megafunction requires only a time-division multiplexing (TDM) clock and a 125-µs frame pulse as inputs, and generates an ST-bus-compatible serial output stream and output frame pulse. A 32-channel ST-bus stream example is shown in Figure 2; the gains synthesized by the GainGen megafunction are placed into the first time slots of the stream.
Figure 2. GainGen Example Timing
For the example shown in Figure 3, gains have been defined with the GainGen MegaWizard Plug-In. The GainGen hardware will synthesize the gains and place them into the 32 time slots of an ST-bus stream.
Figure 3. GainGen WegaWizard Plug-In
Customization: GainGen MegaWizard Plug-In
The GainGen megafunction is fully customizable with respect to the gain levels generated. With the associated GainGen MegaWizard Plug-In, the user can create virtually any gain levels required by the target application. Additionally, the MegaWizard Plug-In allows the user to minimize the number of embedded array blocks (EABs) required to synthesize the gains, by calculating the least number of pulse code modulation (PCM) samples required to generate the desired levels.
Applications
The GainGen megafunction can be used to manage signal gains for a small office/home office PBX system, network switches, digital loop carriers, international voice gateways, and a host of other telecom applications.
Example Application - SOHO PBX System
Generally, telecom lines are engineered to manage a -6 decibel (db) loss, so that standard point-to-point connection loss is managed (as shown in Figure 4.)
Figure 4. Standard Point-to-Point Connection Loss
When the telecom line passes through a PBX, improper gain levels force users to strain to hear external calls and muffle calls within the internal phone network. In a well-balanced network, the correct gain levels are achieved regardless of where the points originate and terminate.
In the application shown in Figure 5, the GainGen software adds 3-db losses to internal calls. Three-party calls, therefore, require a 2-db loss per line to achieve a total loss of 6 decibels. External calls require zero loss on each line as the -6 db loss occurs in the external network.
With the GainGen software, the PBX also can better manage digital phone interfaces such as T1 connections and digital modems, and analog interfaces such as standard voice connections, analog modems, and fax machines.
Figure 5. PBX Using GainGen Software
Device Utilization Example
Table 1 lists the typical device utilization results for the megafunction.
| Table 1. Typical Device Utilization for the Megafunction |
| Gain |
Device |
Speed Grade |
Utilization |
Performance
(fMAX) (2) |
| Logic Cells |
EABs (1) |
| µ-Law8 TDM highways4 gain levels128 timeslots/highway |
FLEX®
EPF10K100 |
-3 |
390 |
5 |
27.24 MHz |
| A-law1 TDM highway8 gain levels32 timeslots/highway |
ACEXTM
EP1K30 |
-1 |
95 |
5 |
60.24 MHz |
| µ-LawA-Law(Law Conversion)4 TDM highways4 gain levels32 timeslots/highway |
ACEX
EP1K50 |
-1 |
226 |
9 |
53.19 MHz |
| Mu-LawA-Law(Law Conversion)12 TDM highways8 gain levels128 timeslots/highway |
FLEX
EPF10K200 |
-1 |
582 |
19 |
35.58 MHz |
Note:
- EABs = Embedded array blocks
- Frequency requirements are dictated by the number of timeslots on the TDM highways. For all examples, the device performance exceeds the requirements for the TDM clocks.
Contact Information
For additional information, you can contact NComm, Inc. at: NComm, Inc.
254 North Broadway
Suite 106
Salem, NH 03079
Tel. (603) 893-6186
Fax (603) 893-6534
E-mail: sales@ncomm.com
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