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MH88422-3 Datasheet(PDF) 3 Page - Mitel Networks Corporation |
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MH88422-3 Datasheet(HTML) 3 Page - Mitel Networks Corporation |
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3 / 14 page  Preliminary Information MH88422 2-15 Functional Description The device is a Data Access Arrangement (D.A.A.). It is used to correctly terminate a 2-Wire analog loop. It provides a signalling link and a 2-4 Wire line interface between an analog loop and the subscriber’s data transmission equipment such as Modems, Facsimiles (Fax’s), Remote Metering and Electronic Point of Sale equipment (EPOS). Isolation Barrier The device provides an isolation barrier implemented by using optocouplers. This is a reinforced barrier for an instantaneous power surge of up to 3kV r.m.s ., for example a lightning strike. It also provides full isolation for a continuous AC voltage level of up to 250V r.m.s. External Protection Circuit Should the input voltage from the line exceed that isolated by the optocoupler, an External Protection Circuit assists in preventing damage to the device and the subscriber equipment. See Figure 3. Line Termination When Loop Control (LC) is at a logic 0, a line termination is applied across Tip and Ring. The device can be considered off-hook and DC loop current will flow. The line termination consists of both a DC line termination and an AC input impedance. When LC is at a logic 1, a Dummy Ringer is applied across Tip and Ring. The device can be considered on-hook and negligible DC current will flow. The dummy ringer is an AC load, which represents a telephone’s mechanical ringer. DC Line Termination When LC is at a logic 0, an active termination is applied across Tip and Ring, at which time it can be considered to be in an off-hook state. This is used to terminate an incoming call, seize the line for an outgoing call, or if it is applied and disconnected at the required rate, can be used to generate dial pulses. This termination resembles approximately 300 Ω resistance, which is loop current dependent. Input Impedance The MH88422 is available in a number of different variants each of which has its own fixed Tip-Ring AC input impedance (Zin). Each variant is identified by the final digit in its part number, as listed below. Also shown are the countries whose PTT requirements match these impedances. MH88422-1 Zin = 220 Ω + 820Ω // 120nF Australia / South Africa / Spain MH88422BD-1 Zin = 220 Ω + 820Ω // 115nF German BABT ZV5 MH88422-2 Zin = 600 Ω North America MH88422-3 Zin = 370 Ω + 620Ω // 310nF UK / New Zealand Many of these countries now pass equipment approved to CTR21. The MH88422 will not meet this specification. See the MH88437 datasheet for a CTR21 Product. Dummy Ringer This device supports a dummy ringer option which can be configured by the inclusion of external components. Further details relating to component values and configuration can be obtained from MSAN-154. For example, Figure 3 shows capacitor C2 which if set to 1.8 µF would meet the New Zealand dummy ringer requirements. 2-4 Wire Conversion The device converts the balanced 2-Wire input, presented by the line at Tip and Ring, to a ground referenced signal at VX, as required by modem/fax chip sets. Conversely the device converts the ground referenced signal input at VR, to a balanced 2-Wire signal across Tip and Ring. During full duplex transmission, the signal at Tip and Ring consists of both the signal from the device to the line and the signal from the line to the device. The signal input at VR, being sent to the line, must not appear at the output VX. In order to prevent this, |
Similar Part No. - MH88422-3 |
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Similar Description - MH88422-3 |
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