Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
The Hx1 & Hx2 use standard RJ-11 type “modular” telephone connectors. Only the two center pins that carry the analog line’s “tip and ring” are used. Connect the telephone line using the rear panel “LINE” jack.
The Hx is designed to work with ordinary “loop start” analog phone lines, though it can operate on PBX extensions and VoIP Analog Terminal Adapters (ATA’s). Hybrid performance and system behavior on these kinds of lines may vary. If you plan to use your Hx on any of these types of lines or connect your unit to other legacy Telos systems such as the Direct Interface Module and others, please see the section on Connecting to Other Systems.
Lines that carry “Shared Line DSL” can be problematic. It’s suggested that you avoid using the Hx on lines that carry DSL, but if you must use one, be sure to use a “line splitter” or DSL filter in series with the “LINE” jack on the Hx.
DSL lines have data carriers above the voice band of the circuit, usually from 25 kHz to 1004 kHz. DSL filters strip away the high-frequency data carriers and pass on the 0-4 kHz voice band and signaling. Some filters are better than others and sometimes better results can be obtained by cascading several filters, each rolling off more of the high-frequency energy. On a line with DSL you might hear more “hiss” and “hash” than with a normal line.
An analog phone set may be plugged into the “PHONE” jack. The telephone can be used when the Hx is “off ”. You might want to disable the telephone’s ringer if you are in a studio environment. The Hx has a “line ringing” open collector output that you can use to light lamps or strobes. For details please see the section on Remote Control.
The Hx has a switchable “auto-answer”. For details, please see the section on Rear Panel DIP Switches.
The SEND IN input connection has the following characteristics:
XLR Pin 1 = Ground
XLR Pin 2 = High (Active balanced, RF suppressed)
XLR Pin 3 = Low (Active balanced, RF suppressed)
Bridging impedance > 100K Ohm
Analog clip point = +24 dBu
Analog-to-Digital converter resolution = 24 bits
Adjustable input level from -10 to +8 dBu
Switchable LINE and MIC level input range
The unit can accommodate a line input level between -10 dBu and +8 dBu, adjustable with a trim pot on the rear panel. The input level is set to +4 dBu level from the factory. A +4dBu signal fed into the SEND IN connector should light the Yellow LED bar graph segment on the Front Panel. If more input gain is needed, turn the trim pot CLOCKWISE to increase the gain and match the operating level of the hybrid.
Note - Increasing the send level beyond a normal meter reading does not increase the level into the telco line due to the hybrid’s AGC and limiting. You will only add distortion and degrade the hybrid’s performance. There is a dip switch configuration option that applies an extra 3dB gain after the AGC should you need more send level. See the section on Rear Panel DIP Switches for details.
Next to the input level pot is a pushbutton switch that selects between line and mic levels. When the pushbutton switch is in the LINE position (out), the input range of the SEND IN signal is –10 to +8 dBu. When the switch is in the MIC position (in), the input range of the SEND IN signal is –70 to –52 dBu.
The inputs are designed to be sourced from balanced lines. Usually, shielded cables have the shield wire connected only on one end (most often at the input) to prevent ground loops. Older equipment with a transformer output stage may need a terminating resistor across Pins 2 and 3 to maintain a proper “flat” frequency response. Consult the manual for your equipment for how to use it with high impedance inputs.
If you are connecting a device with an unbalanced output to your Hx, connect the shield from the output of your device to Pin 1 (ground) on the Hx input, and the “hot” lead from your unbalanced output to Pin 2 (high) on the Hx.
Depending on the device, you might also want to try connecting Pin 3 of the Hx input to ground or “floating” the ground and using only the high and low pins on the Hx.
It’s also important that unbalanced lines be kept short to avoid hum and noise pickup. You’ll probably need to adjust the input gain on the Hx to match the output of your device.
We also suggest that all of your audio equipment be powered from the same AC power source or circuit to prevent ground loops due to the use of multiple grounds. For complete information and suggested wiring and grounding techniques for your studio or recording workstation, please visit the Telos Alliance support page.
The output connection, RCV OUT, has the following characteristics:
XLR Pin 1 = Ground
XLR Pin 2 = High (Active balanced, RF suppressed)
XLR Pin 3 = Low (Active balanced, RF suppressed)
Output impedance < 60 Ohms
Analog clip point = +24 dBu
Digital-to-Analog converter resolution = 24 bits
The nominal output level is fixed at +4 dBu, with +20 dBu headroom to account for the crest factor of some audio signals.
If you are connecting the output of your Hx to a device with an unbalanced input, connect the shield from your device’s unbalanced input to Pin 1 (ground) on the Hx, and the “hot” lead from your device to Pin 2.
It’s important that unbalanced lines be kept short to avoid hum and noise pickup.
We also suggest that all of your audio equipment be powered from the same AC power source or circuit to prevent ground loops due to the use of multiple grounds.
For complete information on suggested wiring and grounding techniques for your studio or recording workstation, please visit the Telos Alliance support page.
The Hx must be fed send-to-caller audio that is free of the caller audio, commonly referred to as a "mix minus" feed. A mix-minus is a mix of all of your audio sources that will be placed on-air (or recorded) except the caller audio – thus the "mix-minus" designation. The European term M-1 (mix-minus one) is perhaps a clearer term. A mix-minus is also sometimes referred to as a ‘clean feed’. The important thing to remember is that the hybrid must not "chase its tail" – the condition that occurs when its output makes its way somehow back to the input.
Hot Tip: Many hybrid installation problems are caused by an inadvertent signal path that forms a loop from the hybrid’s output back to its own input. Some consoles allow this when certain control combinations are selected by the user. In some cases, it may be as simple a mistake as assigning the hybrid to whichever bus is feeding the hybrid. This is the first place to look when strange or erratic performance is experienced. The quickest test is to bring up only the hybrid in question on the board and select a line. Dial tone should not appear on the send meter of the hybrid in question.
Most modern broadcast consoles have provision for multiple mix-minus busses. The best consoles allow selective feeds to the phone system. This is useful since sometimes you want only one microphone feeding the phone, but sometimes you want two, three or four mics (during the morning show, for instance), and sometimes you want to play some audio piece that callers need to hear and react to such as contest sound effects, etc. Some even provide for separate ‘on-air’ and ‘off-line’ (recording) telephone modes.
Consoles made before around 1990 rarely had good support for mix-minuses, and almost never for more than one or two. With one of these oldsters, some clever improvisation is needed.
Here we describe a possible scenario that can be used as a starting point for your situation. We assume an older console with Program and Audition as the main busses. There is another bus of some kind that can be adapted for mix-minus application. We’ll call this the ‘Utility’ bus. All sources, including the hybrid, will be assigned to Program so that the audience can hear them. We will also assign most of these sources to Utility as well, just never the fader with the hybrid’s own audio.
This arrangement is flexible, allowing the operator to place any or all sources in Utility for the caller to hear. In our example we are fortunate in that the console permits the Utility bus to be fed pre-fader, letting the announcer easily use the telephone system for off-air conversations.
A recorder can be attached to the Utility and hybrid outputs to record announcer + phone audio. This is often done as shown here, with each signal to a separate track. One drawback is the potential for the operator to accidentally put the hybrid in Utility, in which case it is no longer a mix-minus. To avoid this error, the signal path could be permanently disconnected by removing the summing resistors or by some such creative operation.
If no bus is available to feed the Hx, you could use an external mixer that bridges the microphone inputs to achieve the same effect.
The Hx2 has multiple hybrids and works best if two faders can be assigned to the telephone system with two associated mix-minuses, one for each telephone line. This is probably not going to be easy with an older console, but the Hx2 has an option to work with a single external mix-minus by making an internal cross-connection of the hybrids. See the section on Hx2 Internal Mix-Minus for details.
A small audio mixer is sometimes used to record interviews from the telephone line using a single hybrid. The mixer’s main bus is fed to the recording device. Both the microphone and the hybrid will be brought up on the faders so the interview can be recorded. Most small mixers (such as those made by Mackie) have one or two Aux send busses, so we will use these to feed the telephone system. We will turn up Aux for the microphone but we will make sure it is turned fully off for each channel that has the corresponding caller audio.
Important: Before connecting your Hx hybrid to any utility mixer, make sure to disable phantom microphone power (if so equipped) from the mixer's mic preamp. Voltage from phantom power will damage the hybrid. Factory repairs to units damaged by phantom power will not be covered under warranty.
Production-style consoles often used for TV audio will have multiple Aux send busses that can be used in a similar way to the small mixer example above. Each hybrid is sent from an Aux bus and everything the caller needs to hear is mixed into that bus, taking care to keep the hybrid itself off the bus.
When on remote, calls are usually received at the studio rather than at the remote site to save money and hassle. In this situation, caller audio must be fed to the remote talent so that they can hear and respond to callers. Moreover, the callers need to hear the talent. In many cases, the remotes are sufficiently distant that talent cannot monitor the station for the caller feed. Even if they could, the profanity delay would be a problem, since the talent needs to hear the callers pre-delay.
All perceptual codecs (such as the Telos Zephyr or X-Stream) and any IP codec have too much delay for talent at remote locations to hear themselves via a round-trip loop. Therefore, another mix-minus is required to feed a codec and the talent hears callers via the codec return path. As before, you feed this return with mix-minus, a mix of everything on the program bus minus the remote audio. As for the second half of the equation, the callers hear the talent because the remote feed is added to the telephone mix-minus bus. This is no problem if you have a set-up that permits selective assignment to the hybrid mix-minus.
One problem with this arrangement is a result of a hybrid with too much leakage combined with the system delay. If the hybrid isn’t doing a good job of preventing the send audio from leaking to its output, the special remote send mix-minus is corrupted. Remember, if any of the announcer audio from the remote site is returned via the monitor feed, it will be delayed by the digital link, causing an echo effect. The Telos Hx really shows its stuff in this situation. Because it has such good trans-hybrid loss, leakage is not at all likely to be a problem. And should there ever be a problem, you can solve it by increasing the amount of ducking.
Note - The Hx has the more common pin-outs used for three-pin XLR inputs and outputs. One trick for remembering the correct pin-out when wiring connectors is to use the phrase "George Washington Bridge." Pin 1 = Ground, Pin 2 = White, and Pin 3 = Black. Note that most mic cables use a white conductor, through some use red.
The two hybrids in the Hx2 unit can be configured so that a single mix-minus feed is used for both hybrids with each hybrid’s output fed into the other’s input internally at unity gain. This way, the callers can hear each other and the outputs are summed with the audio from the console's mix-minus output. Only the SEND IN #1 input is used to feed both hybrids. Both hybrid outputs still function independently. The two hybrid outputs are NOT summed together, so you should provide a fader for each hybrid. The console's mix-minus must be configured so that no hybrid’s output gets sent to its own input.
Figure 4 above illustrates which signals are combined together inside the Digital Signal Processor and routed to each connector when the Hx2 internal mix-minus feature is enabled. Use this option if you only have a single mix-minus available from your console and you wish to use both hybrids to conference callers on the air. You’ll still need a fader for each hybrid output. Bit #6 in the ‘OPTIONS’ DIP switch bank controls the mix-minus feature. The internal mix-minus feature is enabled when the switch is ON. The default factory setting is OFF.
We know that you’re creative and we couldn’t hope to address every possible situation that you face, but armed with a little knowledge about how the Hx works internally, you should be successful with most applications.
In short, the Hx will operate on anything that electrically “looks" like a POTS telephone line, and you can connect it to anything that is designed to run a standard Analog telephone set.
It needs loop current of 15-120 ma at 12-50 volts to run its line interface chip. The chip provides telephone line audio and line signaling status (such as on-hook/off-hook/ringing/loop drop, etc.) to the processor to control the unit. If loop current isn’t present, you’ll have no audio and the Hx will simply hang up, which is the correct behavior.
When connecting to PBX station ports, VoIP Analog Terminal Adapters (ATA's), and even telephone company-provided “pair gain” systems and channel banks, sometimes things can be a little different.
Odd voltages, strange feature implementations, and other issues can cause problems with audio performance and produce weird behavior. Fortunately, these kinds of interfaces keep getting better, meaning that the Hx will probably “just work” - with a few possible exceptions.
The most common issue is likely to be what we call "disconnect supervision": That is, “What the line does when the caller on the line hangs up”. Disconnect supervision is especially important if you intend to use the auto-answer feature. When an “on-air” connected call drops, a wide range of things may happen:
Most PBX’s will simply drop the audio from the outside line and perhaps send a fast busy (or reorder) tone; the Hx will stay off-hook until you manually drop it unless you’ve set the Call Progress Tone Disconnect to disconnect after hearing reorder tone with the internal dip switches.
Some PBX’s will send a momentary loop current interruption that will cause the Hx to release from the line, which is the desired behavior (Congratulations! You’re a winner!); we’ve had good luck with PBX’s from Avaya (Larger systems).
EON/Cortelco, NEC, and station disconnect supervision can be enabled in Mitel digital PBX’s, though it is not set this way by default; most telephone company central office lines do support Calling Party Control (CPC) or loop current interruption-based disconnect.
Most ATA’s used by VoIP providers will simply play a reorder (fast busy) tone; most are capable of sending the CPC loop current interruption signal, though many have this feature disabled by default; it can usually be turned on through the web interface on the unit; the best ones we’ve seen are units made by Cisco/Linksys and Sipura.
Some Foreign Exchange or ‘choke’ lines will not pass the CPC signal and the line will go silent, to dial tone, a reorder, or even a recorded message; this is mainly a function of circuit design and the selection of central office equipment by the telephone company.
Using the Hx - or any hybrid supporting disconnect supervision with the Direct Interface Module (DIM) - requires an external source of loop current. The DIM provides only a “dry” transformer audio feed which worked well with the simpler hybrids of the time. Visit the Telos website or contact support for several options that will allow you to use the Hx with the DIM.
Telos Alliance collects and shares what we learn about “real world” telephony with our customers, who come up with creative ways to use our products and often create elegant solutions for unusual problems. If you need help connecting to a system not covered here, please reach out to our support team.
Likewise, we’d appreciate hearing about your successes and challenges to share with other colleagues and friends. We’re also interested in your experiences with service providers and telecom systems and equipment vendors.
Now that everything is connected, it’s time to check for signs of life!
First, power the unit up and watch it complete its self-test. If the phone line is connected properly, a “dot” should be present on the display. If a minus “-” is displayed, the Hx does not detect the line voltage on the idle POTS line. Check your wiring!
If your Hx is directly connected to a phone line, press the [ON] key and dial tone should be present on the Hx’s output and RCV bar graph.
Next, verify correct mix-minus operation by noting that the RCV bar graph shows the dial tone at a nominal level and that the SND bar graph shows only the microphone or audio present on the device feeding the Hx SEND IN. Remember, the goal of a proper mix-minus is to prevent the hybrid from "hearing itself."
The Hx1 and Hx2 mount in a 1RU space in a standard 19” rack. The unit generates very little heat and needs no special attention for cooling or rack placement. The unit will operate in any environment where the stirred air temperature around the unit is between 0 to 40 degrees Celsius (32 to 104 degrees Fahrenheit) with a relative humidity of 0 to 98% (non-condensing).
AC power is provided via the rear panel IEC power inlet. Hx1 and Hx2 both feature an internal auto-ranging (100-240V, 60/50 Hz) power supply.
Important - Please click here for important information on proper grounding and other items pertaining to electrical safety.
The female DB9 connector on the back panel provides access to control functions. Pin 1 of the DB9 connector is Ground. Pins 2 through 5 on the top row are for GPIO input signals from the remote device, while Pins 6 through 9 on the bottom row are GPIO output signals to the remote device. Two of the GPIO input pins and two of the GPIO output pins are reserved for each hybrid as follows:
Figure 2 below shows an example typically used for triggering an external ring indicator using an external power supply and a common ground between the PSU and Pin 1 of the Hx's remote port.
The GPIO inputs are designed to be universal.
They accept either a voltage source up to 24VDC, or a closure to ground which may be provided by switches, relays, or logic outputs.
In the latter case, either ‘totem-pole’ or open-collector will work.
The inputs are active low.
A built-in 10k Ohm pull up resistor is provided.
Open-collector to ground.
These will require a pull-up resistor to drive TTL-style logic inputs; most equipment has the pull-up built into the input.
If there is no pull-up, you’ll have to add one, connecting it from the output pin to a +5V source; an appropriate value is 2.2K Ohms.
Sink (pull-down) current must be limited to 400mA maximum per output with the total output restricted to 1 amp (250 mA each output if all four will be used).
The GPIO output pins can be used to provide status information to other devices or warning lamps.
Outputs are available to indicate “hybrid in use” and “line ringing”.
Pin Number
Function
1 GPIO
Ground
2 GPI 1
Hybrid #1 - Hybrid ON
3 GPI 2
Hybrid #1 - Hybrid OFF
4 GPI 3
Hybrid #2 - Hybrid ON
5 GPI 4
Hybrid #2 - Hybrid OFF
6 GPO 1
Hybrid #1 - Ringing indicator
7 GPO 2
Hybrid #1 - ON/OFF status indicator
8 GPO 3
Hybrid #2 - Ringing indicator
9 GPO 4
Hybrid #2 - ON/OFF status indicator