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Configuration of the Hx is done via DIP switch settings, and detailed information on their functions and settings is provided in the Rear Panel DIP Switch and Country-Specific Settings sections.
In order to set up your Hx most effectively - especially if this is your first time using the product - a few minutes spent here will help you decide which features will be most beneficial for your particular application.
The Hx1 and Hx2 hybrid’s receive audio processing consists of the following functions:
High-pass “hum” filter
Adaptive Echo Cancellation
Automatic Gain Control
Noise Gate
Digital Dynamic Equalization
Sample rate conversion
This filter removes hum and other unwanted low-frequency noise from the caller audio and has a break frequency of 100 Hz.
An adaptive filter removes studio send audio from the received caller audio. It adapts continuously to preserve a natural sound.
The Hx’s smart gated AGC improves the consistency of the caller’s audio level as delivered to the studio console without audible processing artifacts. An important feature of this AGC is that it is cross-coupled to other sections of the hybrids and can therefore reliably distinguish between caller audio and hybrid leakage. This allows the use of more aggressive gain control for bringing up low-level callers while still preserving excellent hybrid performance.
Enabling the noise gate engages the built-in downward expander which reduces low-level line noise when no caller audio is present and reduces low-level leakage. This function is cross-coupled with the AGC and the ducking system.
Telephone audio frequency response varies widely and is affected by many different factors. making some form of receive equalization desirable. The Hx’s Digital Dynamic EQ is the most sophisticated solution available in a broadcast telephone interface, and all processing is performed in the digital domain. The Receive EQ settings control the type of equalization applied to the receive telephone audio as follows:
Off - Caller audio is passed without modification.
Fixed - A simple manual equalizer.
Adaptive (Digital Dynamic) - A three-band dynamic equalizer in which the frequency breakpoints, time constants, and other characteristics have been chosen to optimize the tonal quality of telephone callers; you set desired target levels to customize the caller's spectral characteristics, and the hybrid maintains the spectral balance from call to call.
Adaptive + Fixed - This mode separately adds a fixed amount of additional gain to the high- and low-frequency bands of the three-band dynamic equalizer.
The Hx1 and Hx2 hybrid's send-to-caller audio processing consists of the following functions:
Sample rate conversion
High-pass filter
Anti-Feedback, consisting of the “pitch” shifter and Acoustic Echo Canceler
AGC/Limiter
AES and analog input sources are sample rate-converted to the hybrid’s internal sampling rate of 48 kHz.
A high-pass filter with a 300 Hz break frequency improves hybrid performance and enhances intelligibility by removing unnecessary low frequencies from the input audio. This filter is always enabled.
The Hx has an Acoustic Echo Canceler (AEC) that improves feedback performance and cancels echo caused by "speaker to mic" acoustic coupling. The Hx also uses a "frequency shifter" - a Telos Alliance innovation - that inserts a small, unnoticeable, shift in frequency to the send audio to prevent feedback buildup when the system is used with open speakers.
The AGC helps maintain consistent audio levels to the caller. This function is always enabled. At moderate levels, it is "AGC-like’" while at higher peak levels it is more "limiter-like". In addition to making levels more consistent to callers, it performs the protection limiting required to meet Telecom regulatory requirements.
The ducking function serves several purposes:
It provides “aesthetic” control over the caller that many programmers prefer and allows the announcer to “override” the caller in a way that sounds natural and appropriate.
It reduces feedback when the Hx is used as a speakerphone in an “open loudspeaker’” situation.
It dynamically improves effective trans-hybrid loss to reduce leakage when necessary.
When the ducking function is enabled, the Hx inserts a controlled loss (reduction in gain) into whichever audio path (send or receive) is not active at the moment. When the caller is speaking, this loss is inserted in the announcer path; when the announcer is speaking, caller gain is reduced.
The effect is "seesaw-like" and normally, the amount of gain reduction is symmetrical. However, if Feedback Reduction is also enabled, the hybrid will have more ducking in the announcer-to-caller direction.
More ducking is typically necessary when using an open loudspeaker. As noted above, ducking helps prevent feedback and reduces the amount of echo returned to the caller.
Exactly how much of this effect is applied is selectable, from Half Duplex (which makes the hybrid operate like a "one-way-at-a-time" speakerphone) to Full Duplex (0 dB) which disables ducking altogether. The default setting is -6 dB.
Figure 1 below illustrates the signal processing chain in both the SEND input to the caller as well as the caller receive to the RCV output path. The ducking system is involved in both processing paths.
The rear panel of the Hx1 and Hx2 chassis contain two banks of DIP switches labeled "Settings" and "Options."
The "Settings" switches (SW1) control the operational levels of various signal processing stages. The "Options" switches (SW2) are used to configure various features. The tables below explain the individual DIP switches:
You can separately specify the level of adjustment in the EQ HI and EQ LO frequency bands when the DDEQ mode is configured for Fixed EQ mode. SETTINGS Bits #1 and #2 control the dB adjustment for the EQ HI band, and Bits #3 and #4 control the dB adjustment for the EQ LO band as follows:
SETTINGS
SETTINGS
We encourage you to try varying levels of EQ boost to make your telephone audio sound warmer and clearer. Our factory default settings should be considered a safe starting point, but because tastes and situations differ, we don’t presume to make those choices for you. Our testing does suggest that utilizing the full 6 db boost works well in most cases and dramatically enhances telephone audio, but we suggest that you set up your phones like you would any other audio processing device: Adjust, listen critically, and repeat the process until you’re satisfied.
SETTINGS
SETTINGS Bits #7 and #8 jointly control the operation of the receive AGC and Noise Gate processing functions. You can select how aggressively low-level signals are brought up to the nominal (+4 dBu) level using the following bit settings:
SETTINGS
OPTIONS Bits #3 and #4 jointly control the operation of the Auto-Answer feature of the hybrid. You can select between turning the feature off, or set the number of rings before the incoming call is answered and then placed on air as follows:
OPTIONS
The Hx1 and Hx2 hybrid units have been designed to send a -9 dBu average level to the telephone line in order to meet the USA’s FCC regulations. OPTION Bit #5 adds 3 dB of gain to the send level heard by the caller. This should only be used when the hybrid is connected to a PBX or in countries outside of the USA that permit a higher transmit level.
OPTIONS
The Hx2 can operate as two independent hybrids or be configured to perform an internal mix- minus between the two hybrids.
The Hx 1 and Hx2 have an optional Acoustic Echo Canceler in the Studio send path. This can be used when there is acoustic coupling between a loudspeaker connected to the hybrid output and a microphone connected to the input. Enabling feedback reduction also causes the ducker to insert more loss into the announcer-to-caller direction when the caller is dominant.
OPTIONS Bit #8 is set aside as RESERVED for future use.
OPTIONS
This figure also shows which processing stages are adjustable via the SETTINGS and OPTIONS bank of DIP switches in the rear of the hybrid unit. See the section on for details.
Options Bits 1 and 2 control the overall operation of the DDEQ processing function. Selections include OFF, Fixed EQ, Adaptive EQ, or Adaptive + Fixed EQ. See the for an explanation of each.
SETTINGS Bits #5 and #6 control the overall operation of the Ducker processing function. See the for an explanation of each setting, including full-duplex (no ducking), -6 dB, -12 dB, or half-duplex (one way at a time).
Settings | Function |
Bits 1 and 2 | EQ LO, fixed dB gain adjustment |
Bits 3 and 4 | EQ HI, fixed dB gain adjustment |
Bits 5 and 6 | Ducking dB gain adjustment |
Bits 7 and 8 | AGC and Noise Gate settings |
Options | Functions |
Bits 1 and 2 | DDEQ configuration |
Bits 3 and 4 | Auto-answer configuration |
Bit 5 | Send gain to phone |
Bit 6 | Hx2 internal mix-minus enable |
Bit 7 | Feedback Reduction enabled |
Bit 8 | Reserved |
Bit 1 | Bit 2 | Setting Value |
OFF | OFF | DDEQ turned OFF |
OFF | ON | DDEQ enabled in Fixed EQ mode (use SETTINGS Bits 1-4 to set levels) |
ON | OFF | DDEQ enabled in Adaptive EQ mode (factory default setting) |
ON | ON | DDEQ enabled in Adapt + EQ mode (use SETTINGS Bits 1-4 to set levels) |
Bit 1 | Bit 2 | Setting Value |
OFF | OFF | EQ LO, 0 dB adjustment (factory default setting) |
OFF | ON | EQ LO, +2 dB adjustment |
ON | OFF | EQ LO, +4 dB adjustment |
ON | ON | EQ LO, +6 dB adjustment |
Bit 3 | Bit 4 | Setting Value |
OFF | OFF | EQ HI, 0 dB adjustment (factory default setting) |
OFF | ON | EQ HI, +2 dB adjustment |
ON | OFF | EQ HI, +4 dB adjustment |
ON | ON | EQ HI, +6 dB adjustment |
Bit 5 | Bit 6 | Setting Value |
OFF | OFF | Full Duplex (no attenuation) |
OFF | ON | -6 dB attenuation (factory default setting) |
ON | OFF | -12 dB attenuation |
ON | ON | Half Duplex |
Bit 7 | Bit 8 | AGC Setting Value | Noise Gate Setting Value |
OFF | OFF | Phone AGC = OFF | Noise Gate = OFF |
OFF | ON | Phone AGC = 1/2 Full | Noise Gate = OFF |
ON | OFF | Phone AGC = Full | Noise Gate = OFF (factory default setting) |
ON | ON | Phone AGC = Full | Noise Gate = Normal |
Bit 3 | Bit 4 | Auto-Answer Setting Value | Ring Setting Value |
OFF | OFF | Auto-answer = OFF | Disabled (factory default setting) |
OFF | ON | Auto-answer = ON | Auto-answer after first ring |
ON | OFF | Auto-answer = ON | Auto-answer after third ring |
ON | ON | Auto-answer = ON | Auto-answer after eighth ring |
Bit 5 | Setting Value |
OFF | No additional gain applied (factory default setting) |
ON | +3 dB additional gain applied to audio sent to the caller |
Bit 6 | Setting Value |
OFF | Independent - Internal mix-minus disabled (factory default setting) |
ON | Coupled - Internal mix-minus enabled |
Bit 7 | Setting Value |
OFF | Acoustic Echo Canceler disabled (factory default setting) |
ON | Acoustic Echo Canceler enabled (use in "open speaker" situation) |
Bit 8 | Setting Value |
OFF | Reserved for future use (factory default setting) |
ON | Not recommended |
There is a third bank of DIP switches located inside the Hx chassis used to set country-specific voltage and line impedance settings and to set the Call Progress Tone to be detected if Call Progress Tone Disconnect is used.
The Factory Default setting is all 8 bits set to the OFF position (labeled OPEN on the switch). This default configuration is set for operation within the United States and Canada (North American telephone line characteristics, and the ‘precise’ dial-tone signal for Call Progress Tone Disconnect).
You must remove the top cover of the chassis to gain access to the third bank of DIP switches located on the Hx motherboard.
Important! The chassis cover should only be removed by a qualified technician. AC power must be disconnected prior to removing the cover.
The internal DIP switch bank is divided up into two subsets of 4 switches each:
Bits 1 through 4 configure the Hx’s telephone interface circuitry to match the telephone line impedance and voltage characteristics of the country where the hybrid is used.
Bits 5 through 8 configure Call Progress Tone Detection to match the call progress tones used by various countries or central office switches.
Call progress tones (Dial tone, busy tone, etc) can be used to make the Hx disconnect when loop current signaling is not available or is unreliable.
Call Progress Tone Disconnect is active only on Auto-Answered incoming calls to prevent undesired disconnections; it may be disabled if the feature causes problems in your application; see internal DIP switch settings table below.
Table 1 below provides details of network characteristics. Table 2 deals with Call Progress Tone Detection. Table 3 lists the recommended DIP settings for each country.
Note that the term "re-order tone" refers to the "fast busy" signal often used to indicate network congestion or an error condition.
TABLE 1 - Network Characteristics (Bits 1 - 4)
TABLE 2 - Call Progress Tone Detection Settings (Bits 5 - 8)
TABLE 3 - Settings for Countries (Bits 1 - 8)
Bit 1 | Bit 2 | Bit 3 | Bit 4 | Bit 5 | Bit 6 | Bit 7 | Bit 8 |
SETTINGS | OFF | OFF | OFF | OFF | OFF | ON | ON | OFF |
Bits | Setting | Value |
Bits 1 & 2 | EQ LO, fixed dB gain adjustment | 0 dB gain |
Bits 3 & 4 | EQ HI, fixed dB gain adjustment | 0 dB gain |
Bits 5 & 6 | Ducker dB gain adjustment | -6 dB ducking |
Bits 7 & 8 | AGC and Noise Gate Settings | AGC FULL, Noise Gate OFF |
Bit 1 | Bit 2 | Bit 3 | Bit 4 | Bit 5 | Bit 6 | Bit 7 | Bit 8 |
OPTIONS | ON | OFF | OFF | OFF | OFF | OFF | OFF | OFF |
Bits | Setting | Value |
Bits 1 & 2 | DDEQ configuration | Dynamic EQ enabled |
Bits 3 & 4 | Auto-Answer configuration | OFF |
Bit 5 | Send gain to phone | OFF |
Bit 6 | Hx2 internal mix-minus enable | OFF |
Bit 7 | Feedback Reduction enabled | OFF |
Bit 8 | Reserved | N/A |
Bit 1 | Bit 2 | Bit 3 | Bit 4 | Bit 5 | Bit 6 | Bit 7 | Bit 8 |
INTERNAL | OFF | OFF | OFF | OFF | OFF | OFF | OFF | OFF |
Bits | Setting | Value |
Bits 1 - 4 | Telephone Network configuration | USA, Canada |
Bits 5 - 8 | Call Progress Tone Detection | USA dial tone |
Bit 1 | Bit 2 | Bit 3 | Bit 4 | Telephone Network |
OFF | OFF | OFF | OFF | USA, Canada |
OFF | OFF | OFF | ON | Japan, low voltage networks |
OFF | OFF | ON | OFF | FCC-compliant countries |
OFF | OFF | ON | ON | CRT21, Europe (real line impedance) |
OFF | ON | OFF | OFF | Custom country configuration |
OFF | ON | OFF | ON | Custom country configuration |
OFF | ON | ON | OFF | Custom country configuration |
OFF | ON | ON | ON | Europe (complex line impedance) |
ON | OFF | OFF | OFF | Custom country configuration |
ON | OFF | OFF | ON | Custom country configuration |
ON | OFF | ON | OFF | Custom country configuration |
ON | OFF | ON | ON | Reserved for future use |
ON | ON | OFF | OFF | Reserved |
ON | ON | OFF | ON | Reserved |
ON | ON | ON | OFF | Reserved |
ON | ON | ON | ON | Reserved |
Bit 5 | Bit 6 | Bit 7 | Bit 8 | CPTD Characteristics |
OFF | OFF | OFF | OFF | U.S. dial tone |
OFF | OFF | OFF | ON | U.S. re-order signal |
OFF | OFF | ON | OFF | WORLD single-frequency dial tone |
OFF | OFF | ON | ON | WORLD re-order, ON = 155 - 550ms, OFF = 155-550ms |
OFF | ON | OFF | OFF | WORLD re-order, ON = 250 - 1,200ms, OFF = 250 - 1,200 ms |
OFF | ON | OFF | ON | WORLD, multi-tone dial tone |
OFF | ON | ON | OFF | WORLD, multi-tone dial tone |
OFF | ON | ON | ON | WORLD, pulse dial tone, ON = 150 - 350ms, OFF = 450 = 1,100ms |
ON | OFF | OFF | OFF | WORLD, pulse dial tone, ON = 100 = 250ms, OFF = 200 - 400ms |
ON | OFF | OFF | ON | Reserved for future use |
ON | OFF | ON | OFF | Reserved |
ON | OFF | ON | ON | Reserved |
ON | ON | OFF | OFF | Reserved |
ON | ON | OFF | ON | Reserved |
ON | ON | ON | OFF | Reserved |
ON | ON | ON | ON | CPTD feature disabled |
Country | Bit 1 | Bit 2 | Bit 3 | Bit 4 | Bit 5 | Bit 6 | Bit 7 | Bit 8 |
Argentina | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Australia | ON | OFF | OFF | ON | OFF | OFF | ON | ON |
Austria | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Bahrain | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Belgium | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Brazil | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Bulgaria | OFF | ON | ON | ON | OFF | ON | ON | ON |
Canada | OFF | OFF | ON | OFF | OFF | OFF | OFF | OFF |
Chile | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
China | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Columbia | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Croatia | OFF | ON | ON | ON | OFF | ON | ON | ON |
CTR21 | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Cyprus | OFF | ON | ON | ON | OFF | ON | OFF | ON |
Czech Republic | OFF | ON | ON | ON | OFF | OFF | ON | OFF |
Denmark | OFF | OFF | ON | ON | OFF | OFF | ON | ON |
Ecuador | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Egypt | OFF | OFF | OFF | ON | OFF | ON | OFF | OFF |
El Salvador | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Finland | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
France | OFF | OFF | ON | ON | OFF | ON | OFF | OFF |
Germany | OFF | OFF | ON | ON | OFF | OFF | ON | ON |
Greece | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Guam | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Hong Kong | OFF | OFF | ON | OFF | OFF | OFF | OFF | OFF |
Hungary | OFF | OFF | ON | OFF | OFF | OFF | ON | ON |
Iceland | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
India | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Indonesia | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Ireland | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Israel | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Italy | OFF | OFF | ON | ON | OFF | OFF | ON | ON |
Japan | OFF | OFF | OFF | ON | OFF | ON | OFF | OFF |
Jordan | OFF | OFF | OFF | ON | OFF | OF | ON | OFF |
Kazakhstan | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Kuwait | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Latvia | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Lebanon | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Luxembourg | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Macao | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Malaysia | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Malta | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Mexico | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Morocco | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Netherlands | OFF | OFF | ON | ON | OFF | OFF | ON | ON |
New Zealand | OFF | ON | ON | OFF | OFF | OFF | ON | OFF |
Nigeria | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
North Korea | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Norway | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Oman | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Pakistan | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Peru | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Philippines | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Poland | ON | OFF | OFF | OFF | OFF | OFF | ON | OFF |
Portugal | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Romania | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Russia | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Saudi Arabia | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Singapore | OFF | OFF | ON | OFF | OFF | OFF | ON | ON |
Slovakia | OFF | OFF | ON | OFF | OFF | ON | ON | ON |
Slovenia | ON | OFF | OFF | OFF | OFF | ON | ON | ON |
South Africa | ON | OFF | ON | OFF | OFF | OFF | ON | OFF |
South Korea | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |
Spain | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Sweden | OFF | OFF | ON | ON | OFF | ON | OFF | OFF |
Switzerland | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
Syria | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Taiwan | OFF | OFF | OFF | ON | ON | OFF | OFF | OFF |
Thailand | OFF | OFF | OFF | ON | OFF | OFF | ON | OFF |
Turkey | OFF | OFF | ON | ON | OFF | OFF | ON | OFF |
UAE | OFF | OFF | ON | OFF | OFF | OFF | OFF | OFF |
United Kingdom | OFF | OFF | ON | ON | OFF | ON | OFF | ON |
USA | OFF | OFF | ON | OFF | OFF | OFF | OFF | OFF |
Yemen | OFF | OFF | ON | OFF | OFF | OFF | ON | OFF |