Telephone interface


£1,290.00 Price excludes VAT

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Comrex’s Digital Hybrid series are high quality single- and dual-line telephone interfaces. Designed to interconnect a standard telephone line and your audio equipment, the DH Series enables users to send and receive audio from a connected telephone line. When the very best audio quality is required for talk shows, news feeds, production, recording studios, or internet applications, these digital hybrids are ideal.

With DSP technology the DH22 delivers the deepest and most stable hybrid null, ensuring maximum isolation between the send and caller audio. This means no echo or “bottom of the barrel” sound.

Additionally, the  DH22 comes with selectable automatic gain control (AGC) and caller ducking. With AGC, each call will be delivered to the equipment at the same level. Caller ducking reduced the caller’s audio level when the announcer speaks, providing a more “controlled” environment. Additionally, we’ve added a speaker amplifier, so you can connect a speaker directly to the unit and monitor callers without headphones.

Key Feature

  • DSP digital technology ensures the very best audio quality and the deepest, most reliable hybrid null
  • Built-in speaker amplifier
  • 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


  • Mic or line input
  • Automatically accepts all worldwide voltages
  • Worldwide compliant, including FCC, CSA, CE and CTR21
  • Dry line capability (U.S. version only)
  • Balanced audio in and out
  • Caller Output: XLR male, 0dBu nominal, adjustable, balanced, 50 Ohm impedance
  • Aux Output: XLR male, 0dBu nominal, adjustable, balanced, 50 Ohm impedance
  • Telco Line: RJ-11 connector, POTS line or analog extension from a PBX or dry line (no DC offset voltage)
  • Telco Set: RJ-11 connector
  • 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
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
  • Distortion: <0.1%
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
  • Distortion: <0.1%
  • Caller-to-Send separation: 50 dB nominal
  • Tail time: 32 milliseconds
  • 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
  • Send-to-Caller separation: 55dB nominal
  • Tail time: 32 milliseconds
Power & Physical
  • Power: IEC Type, Auto Adjusting 100-240VAC, 2A, 50/60Hz, 30W
  • Size: 17.125″ L x 10.125″ D x 1.75″ H (43.6 cm x 25.7 cm x 4.44 cm)
  • Weight: 6.35 lbs (2.88 kg)
  • Operating Temperature: 32-100° F (0-38° C)
  • Humidity: 0-80 percent