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Comrex DH20
Digital Hybrid Single Line Telephone Interface


The DH20 is a high quality single line telephone interface that interconnects a standard telephone line and your audio equipment...
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Our Price: $1,074.60
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Comrex DH20
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The DH20 is a high quality single line telephone interface that interconnects a standard telephone line and your audio equipment, allowing you the ability to send audio to and receive audio from a connected telephone line. The DH20 is ideal when the very best audio quality is required for talk shows, news feeds, production, recording studios, and internet applications.

Comrex's newest DSP technology delivers better and more reliable sound quality. The DH20 delivers the deepest and most stable hybrid null, ensuring maximum isolation between the send and caller audio. That means no echo and no "bottom of the barrel" sound.

In addition, Comrex has added selectable automatic gain control(AGC) and caller ducking. With AGC, each call will be delivered to your equipment at the same level. Caller ducking reduces the caller's audio level when the announcer speaks, providing a more "controlled" environment. There's also a speaker amplifier so you can connect a speaker directly to the unit and monitor callers without headphones.


  • DSP digital technology ensures the very best audio quality and thedeepest, most reliable hybrid null
  • Easy to install, simple to operate
  • Built-in speaker amplifier
  • Balanced audio in and out
  • Mic or line input
  • Selectable AGC ensures every caller is at the same audio level
  • Selectable caller ducking
  • Selectable auto-answer/auto-disconnect compatible with most telephonecentral offices including loop current interruption and busy/reorder tones
  • Remote control and status
  • Automatically accepts all worldwide voltages
  • Worldwide compliant, including FCC, CSA, CE and CTR21
  • Dry line capability


  • Caller Output: XLR male, 0dBu nominal, adjustable, balanced, 50½ impedance
  • Aux Output: XLR male, 0dBu nominal, adjustable, balanced, 50½ impedance
  • Telco Line: RJ-11 connector
       POTS (plain old telephoneservice) line or analog extension from a PBX or dry line (no DC offsetvoltage).
       A-Lead supervision provided
  • Telco Set: RJ-11 connector, A-Lead supervision provided
  • Telephone Transmit:
       Nominal send input of 0 dBureferenced to -15 dBu onto the telephone line.
       FrequencyResponse: 250 Hz to 3.5 kHz, ±1dB
       Signal to noise ratio:>56 dB
       Distortion: <0.2%
  • Telephone Receive:
       Nominal telephone line level of -15dBu referenced to caller output of 0 dBu
       Frequency Response:250 Hz to 3.5 kHz, ±1 dB
       Signal to noise ratio: >56dB
       Distortion: <0.2%
  • Remote: DB-25 Female
       Remote Send Input: 0dBu nominal,adjustable, unbalanced, 20k Ohm impedance
       Remote Caller andAux Output: 0dBu nominal, adjustable, unbalanced, 50 Ohmimpedance
       Control Inputs: Remotely activate any of thefollowing functions with a switch closure to ground: On, Off, and MonitorMute
       Status Outputs: Remotely check the status of the hybrid using the On and Off status outputs. Status outputs are open collector outputs rated at 30VDC and 40mA maximum
  • Monitor Output: 1/4" stereo jack, Tip=+phase, Ring=ground, Sleeve=ground, 1W output into an 8 Ohm load
  • Send Input: XLR female, Mic/Line selectable, -55/0 dBu nominal, adjustable, balanced, bridging, 20k Ohm impedance
  • Mix-Minus, Caller-to-Send separation: 50 dB nominal, Tail time: 32 milliseconds
  • Operating Temperature: 32-100°F/0-38°C
  • Humidity: 0-80 percent
  • Controls: On/Off Buttons, Volume Up/Down Buttons
  • Status LEDS: On Status, Off Status, Send Audio Presence, Caller Audio Presence
  • Adjustments: Send Input Level, Caller Output Level, Auxiliary Input Level, Auxiliary Output Level, Burst Adapt Select, Mic/Line Select, Caller Boost Select, Momentary/Latching Select, Auto Answer/Disconnect Select, Caller Control Select (0, 6, 12, or 18 dB), AGC Select, Auto Mix-Minus Select, Aux Mix Select
  • Power: IEC Type, Auto Adjusting 100-240VAC, 2A, 50/60Hz, 30W
  • Null, Send-to-Caller separation: 55dB nominal, Tail time: 32 milliseconds
  • Dimensions (W x D x H): 17.125" x 10.125" x 1.75" (43.6 x 25.7 x 4.44 cm)
  • Weight: 6.35 lbs. (2.88 kg)

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