Sonifex CM-TLL

Line Powered Telephone Line Listen Unit

The Sonifex CM-TLL provides a low-loss interface to receive audio from a telephone line.

SKU: 101489



Sonifex CM-TLL

CM-TLL Line Powered Telephone Line Listen Unit

The CM-TLL provides a low-loss interface to receive audio from a telephone line. The line-powered unit is compatible with all analogue direct exchange lines and includes an LED indication of incoming calls. The unit is intended to be used with an earpiece amplifier to receive an audio feed by telephone from a studio.

The line and telephone set are connected to the unit via the RJ11 connectors in order to make an outgoing call. A telephone may not be required if calls are only incoming, because telephone line ringing is indicated by a flashing LED built into the unit. In either case, the ‘LINE CONNECT’ switch is pressed to make the line connection. The ‘ON’ LED indicates that the unit is powered and that audio is routed from the line to the XLR plug.

Features of the CM-TLL

  • Audio interface to direct analogue exchange lines – receive calls with electrical isolation from the line.
  • Line powered, requiring no battery or external power.
  • LEDs indicating ‘Ring’ and ‘On Hold’ conditions.
  • Loop-through line sockets provide in-line connection with existing telephone.
  • The existing telephone remains connected when the unit is in use.
  • Line connections to British or International sockets via supplied cable kit.
  • Connection to the telephone set is maintained while the unit is in use.
  • Small, rugged extruded aluminium case with XLR3 male 4-wire connector.


Technical Specification For CM-TLL

4-Wire Output

Output Impedance: 150 Ω, transformer coupled
Output Connector: 3 pin XLR male connector
Output Level: Typically, 0dBU for average line level


Off Hook Voltage: 6V minimum
2 Wire Connectors: RJ11 socket – line
RJ11 socket – handset

Front Panel Operational Controls

Line Connect: Push button with indicator
Ring LED: Indicates incoming ringing
On LED: Indicates connection to the telephone line

Equipment Type

CM-TLL Line powered telephone line listen unit

Physical Specification

Dimensions: 77 mm (W) x 83 mm (D) x 42 mm (H)
3.0” (W) x 3.3” (D) x 1.7” (H)
Weight: Nett: 0.20 kg Gross: 0.70 kg
Nett: 0.50lbs Gross: 1.6lbs