DISCONTINUED Comrex DH20 Digital Hybrid

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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.

The 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 mean no echo and no “bottom of the barrel” sound.

In addition, selectable automatic gain control (AGC) and caller ducking has been added. 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. A speaker amplifier has also been added so you can connect a speaker directly to the unit and monitor callers without headphones.


The world’s best, most affordable digital hybrid

  • DSP digital technology ensures the very best audio quality and the deepest, 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 telephone central 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

Technical Specification

Technical Specification

Caller Output: XLR male
0dBu nominal, adjustable, balanced, 50 impedance

Aux Output: XLR male
0dBu nominal, adjustable, balanced, 50 impedance

Telco Line: RJ-11 connector
POTS (plain old telephone service) line or analog extension from a PBX or dry line (no DC offset voltage).
A-Lead supervision provided

Telco Set: RJ-11 connector
A-Lead supervision provided

Telephone Transmit
Nominal send input of 0 dBu referenced to -15 dBu onto the telephone line.
Frequency Response: 250 Hz to 3.5 kHz, 1dB
Signal to noise ratio: >56 dB
Distortion: <0.2%

Telephone Receive
Nominal telephone line level of -15 dBu referenced to caller output of 0 dBu
Frequency Response: 250 Hz to 3.5 kHz, 1 dB
Signal to noise ratio: >56 dB
Distortion: <0.2%

Remote: DB-25 Female
Remote Send Input:
0dBu nominal, adjustable,
unbalanced, 20k Ohm impedance
Remote Caller and Aux Output:
0dBu nominal, adjustable,
unbalanced, 50 Ohm impedance
Control Inputs:
Remotely activate any of the following functions with a switch closure to ground: On, Off, and Monitor Mute
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

Caller-to-Send separation: 50 dB nominal
Tail time: 32 milliseconds

Operating Temperature

0-80 percent

On/Off Buttons
Volume Up/Down Buttons

Status LEDS
On Status, Off Status
Send Audio Presence
Caller Audio Presence

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

Send-to-Caller separation: 55dB nominal
Tail time: 32 milliseconds

Dimensions (LxDxH)
17.125″ x 10.125″ x 1.75″
43.6 x 25.7 x 4.44 cm

6.35 lb/2.88 kg (dry)
10.95 lb/4.97 kg (shipping)

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