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Model 272 Telecom Interface with Smart Disconnect

Model 272 Telecom Interface with Smart Disconnect


The Model 272 Telecom Interface with Smart Disconnect is designed to allow equipment ports intended for connection to ground start trunk circuits to be interfaced with loop start trunk circuits. Examples of equipment that can benefit from the Model 272’s capabilities include PBX, automatic call distributor (ACD), and voice mail systems. The loop start trunk circuits that need to be interfaced are typically provided as standard central office (CO) loop start trunks or off-premise extensions (referred to as OPS or OPX circuits) from a PBX system. The unit provides four independent conversion circuits. The Model 272 is intended to be installed at the customer premises, adjacent to the equipment containing the ground start trunk ports.

Model 272 features include LED status indicators, universal powering, and simple installation. Power and individual circuit active LEDs are provided. The Model 272 can be powered with 24 Vac, –24 Vdc, or –48 Vdc. There are no switches to set or straps to cut. The Model 272 automatically adjusts for the power that is connected. The unit is completely self-contained in a wall-mounted cabinet. Interconnections are made using a standard 25-pair telephone-type plug. This method provides simple, time-efficient installation and maintenance.

The Model 272 Telecom Interface with Smart Disconnect is intended to serve as a useful “building block” for special applications. A typical application is to allow the interfacing of PBX off-premise extensions to a voice mail or ACD system. It is common for this scenario to arise as often voice mail and ACD systems are compatible only with ground start trunk circuits. Another common application arises when linking one PBX to another PBX. One PBX provides off-premise extensions while the other PBX only has ground start trunk ports available.

The Model 272 is designed to allow equipment ports intended for connection to ground start trunks to be used with loop start trunk circuits. Model 272 circuits cannot be connected to give the opposite function. If you need to connect loop start equipment ports to ground start trunk circuits, use the Gordon Kapes, Inc. GS-1 Loop Start to Ground Start Converter.

Model 272 Specifications

Number of Conversion Circuits: 4

Ringing Voltage: 60-150 Vac, 16-68 Hz

Ringing Detect Time: 100 milliseconds (nominal)

Circuit Release after Ringing Time: 6 seconds (nominal)

Minimum Ring Load Current: 12 mA

Loop Current Detect Time: 10 milliseconds (nominal)

Loop Current Disconnect Time: 375 milliseconds (nominal)

Maximum Loop Resistance: limited by loop start trunk loop limit

Environment: 0 to 50 degrees C, humidity to 95% (no condensation)

FCC Registration:
Registration Number: BVV8VH-19259-OT-N
Ringer Equivalence: 1.0 B

Radiated Noise Compliance: contains no circuitry subject to EMI regulations

Reliability: MTBF 27.8 years, per Method 1 of Bellcore TS-TSY-000332, Issue 3, September 1990

Interconnections: one 25-pair plug; installer must supply one cable terminated with 25-pair connector

Power Requirement: 18 to 30 Vac, 100 mA maximum Class 2 power transformer only, minimum 5 VA rating –22 to –56 Vdc, 75 mA maximum

8.75 inches high (22.2 cm)
8.75 inches wide (22.2 cm)
3.25 inches deep (8.3 cm)

Mounting: wall mounts with four #8 pan-head screws

Weight: approximately 2 pounds (0.9 kg)


Specifications subject to change without notice.


Additional Information:



Data Sheet

Technical Practice - Preliminary


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