MC33121P - Low-Voltage SLIC Interface | Motorola | PBX
MPN: MC33121P ✓ AktifMC33121P Genel Bakış
A Subscriber Line Interface Circuit, or SLIC, is an integrated telecommunications interface that replaces many discrete functions associated with a analog telephone line. In the broader hierarchy, it is a specialized line interface IC within interface ICs and telecommunications semiconductors. It bridges a central-office or PBX voice path and a subscriber loop while separating transmit and receive signals, supporting line termination, and exposing hookswitch and fault information to the surrounding codec or control electronics.
The MC33121P integrates several line-facing functions into one device. Battery feed supplies the line, while proper loop termination establishes the intended AC impedance seen by the subscriber. Adjustable transmit, receive, and transhybrid gains allow the surrounding system to control voice-path levels and balance. Hookswitch detection reports line activity, and separate status outputs indicate single or double faults, reducing the number of external discrete monitoring elements.
Transmit and receive signals are referenced to analog ground, while digital status and control signals are referenced to digital ground. This separation simplifies interconnection with codecs, filters, and digital control logic. The hookswitch and fault outputs are compatible with TTL/CMOS, and the power-down input permits local shutdown. These interface features make the MC33121P suitable for integrated access, subscriber-line, PBX, voice codec, and central-office interface designs.
Typical uses include a PBX line card, a central-office subscriber interface, a two-wire telephone-line interface, a voice codec interface, a hookswitch monitor, and a line-fault indication circuit. In each case, the IC provides the physical subscriber-line interface while external circuitry handles codec conversion, call control, supervision, and system-level power management. Because this legacy device is a through-hole 14-pin DIP, it is most practical for legacy designs, repair assemblies, and industrial or telecommunications equipment that can accommodate through-hole leaded components.
Designers should preserve separate analog and digital grounding paths and connect the device to the selected codec, filter, and line-conditioning network exactly as shown in the manufacturer application material. Before production use, verify the unavailable operating voltage, temperature range, loop-current limits, external-component values, and absolute maximum ratings against the manufacturer datasheet. Those parameters are not supplied in the verified excerpts and therefore cannot be safely inferred.
This page consolidates verified distributor pricing, package information, interface functions, comparison fields, and practical implementation cautions. It also distinguishes documented MC33121P characteristics from unverified alternatives, avoiding unsupported claims that a different SLIC is truly pin-to-pin compatible.
Drop-in alternatifler için MC33121P — aynı paket, pin-başına uyumlu. PCB yeniden montajı gerektiren farklı paket bileşenleri dışlanmıştır.
Bu ürüne yer değiştirme seçenekleri mevcut değil.
Alternatifleri Talep EdinMC33121P Özellikler
| Product Type | Low-Voltage Subscriber Line Interface Circuit (SLIC) |
| Central-Office Interface | 4-wire side |
| Subscriber-Line Interface | 2-wire subscriber line |
| Battery Feed | Provided |
| Loop Termination | Proper AC impedance |
| Hookswitch Detection | Provided |
| Transmit Gain | Adjustable |
| Receive Gain | Adjustable |
| Transhybrid Gain | Adjustable |
| Fault Outputs | Single and double fault indication |
| Status Output Compatibility | TTL/CMOS compatible |
| Power-Down Input | Permits local shutdown |
| Analog Signal Reference | Analog ground |
| Digital Signal Reference | Digital ground |
| Minimum Longitudinal Balance | 58 dB |
| Paket | 14-PDIP |
| Pin Sayısı | 14 pins |
| Montaj Türü | Through-hole |
MC33121P 14-pdip Pin Yapısı Kılavuzu
MC33121P (14-pdip paket) için pin yapısı. Pin numaralandırma, işlevleri ve bağlantı şemaları üretici veri kitapçığında tanımlanmıştır. Doğru ayak ve soldurma kılavuzları için onu referans alın.
Ayrıntılı pin çıkış verisi mevcut değil: MC33121P.
Aşağıdaki veri sayfası tam pin konfigürasyonu için.
Tipik Uygulamalar
MC33121P için uygundur 6 uygulamas: PBX Subscriber Line Card, Central Office Subscriber Interface, Two-Wire Telephone Line Interface, Voice Codec Interface, Hookswitch and Line Supervision, Line Fault Monitoring.
PBX Subscriber Line Card
The MC33121P fits the subscriber-facing section of a legacy PBX line card because it bridges the four-wire central-office side with a two-wire subscriber line. It supplies battery feed, establishes the proper AC loop termination, detects hookswitch activity, and provides adjustable transmit, receive, and transhybrid gains. These functions allow the line card to concentrate subscriber-facing circuitry while an external codec performs voice conversion. The documented minimum longitudinal balance of 58 dB supports interference rejection on the balanced line path. Engineers should verify the unavailable supply-voltage, loop-current, and temperature limits against the manufacturer datasheet before qualifying the card for a new deployment.
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Central Office Subscriber Interface
The MC33121P is designed for central-office equipment that terminates a two-wire subscriber line while presenting a four-wire interface to switching and codec circuitry. Its integrated battery-feed function, AC loop termination, hookswitch detection, and adjustable voice-path gains reduce the number of separate line-interface blocks. Transmit and receive signals are referenced to analog ground, while digital supervision uses digital ground, simplifying integration with codecs and filters. The fault outputs also support line-card supervision. Because the verified excerpts do not provide maximum loop voltage, current, or timing values, a central-office design should use the manufacturer datasheet to confirm protection, operating-region, and system-timing requirements before release.
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Two-Wire Telephone Line Interface
The MC33121P provides the physical interface for a two-wire telephone subscriber line by combining battery feed, AC loop termination, hookswitch detection, and adjustable transmit, receive, and transhybrid gains. The circuit can sit between the line pair and a four-wire codec path in fixed-line voice equipment. Its documented 58 dB minimum longitudinal balance helps maintain balanced signaling and reduce longitudinal interference. Analog transmit and receive references use analog ground, allowing the analog voice path to remain distinct from digital control signals. The verified material does not provide the external resistor and capacitor values or exact gain-adjustment range, so designers must reproduce the manufacturer reference configuration rather than infer component values.
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Voice Codec Interface
The MC33121P is suitable as the line-side companion to a four-wire voice codec because it separates subscriber-line functions from the codec-facing analog signals. Transmit and receive signals are referenced to analog ground, which simplifies routing toward codec and filter networks, while hookswitch, fault, and shutdown functions can connect to digital control logic. The status outputs are TTL/CMOS compatible. Using the MC33121P this way avoids duplicating battery feed, loop termination, and gain controls at the line card. However, the supplied excerpts do not identify a specific codec MPN or specify codec interface levels, so the actual codec must be selected and reviewed against the complete MC33121 datasheet and reference circuit.
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Hookswitch and Line Supervision
The MC33121P supports hookswitch and line-supervision designs by detecting subscriber-line activity and exposing a dedicated hookswitch status output to TTL/CMOS-compatible control logic. This allows a codec, processor, or call-control circuit to identify line state without implementing a separate mechanical-contact sensing network. The device also includes single and double fault outputs, enabling supervisory logic to distinguish operating abnormalities. Its power-down input provides a further mechanism for controlled local shutdown. The verified excerpts do not include logic thresholds, switching timing, or debounce behavior, so a supervision design should verify those details and test across the intended line current and temperature range before deployment.
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Line Fault Monitoring
The MC33121P can serve as the front end of a line-fault monitoring circuit because it provides single and double fault indications alongside normal hookswitch status. The line interface remains active while the supervision outputs report conditions to TTL/CMOS-compatible control circuitry, reducing the number of discrete sensing stages around the subscriber loop. The separate analog-ground and digital-ground references help keep fault-control paths distinct from the transmit and receive voice path. Since the verified material provides no fault-detection thresholds, response timing, or recovery behavior, engineers should treat the indication logic as datasheet-defined rather than infer it from the status labels and verify it with the intended line and protection networks.
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Önerilen Ürünler Özeti
Mühendislik referans verileri: MC33121P — karşılaştırma, tasarım rehberi ve uyumluluk bilgileri.
Seçim Kılavuzu
Alternatiflerle Karşılaştırma
| Parametre | Bu Ürün |
|---|---|
| Product Type | Low-Voltage Subscriber Line Interface Circuit (SLIC) |
| Central-Office Interface | 4-wire side |
| Subscriber-Line Interface | 2-wire subscriber line |
| Battery Feed | Provided |
| Loop Termination | Proper AC impedance |
| Gain Control | Adjustable transmit, receive, and transhybrid gains |
| Supervision Outputs | Hookswitch and single/double fault indication |
| Control Compatibility | TTL/CMOS-compatible status outputs and power-down input |
| Minimum Longitudinal Balance | 58 dB |
| Package | 14-PDIP |
| Brand | Motorola |
| Verified Reference Price | $1.6197 as of 2026-10-29 |
Ana Farklılayıcılar
- Integrated subscriber-line functions (karşılaştırma:MC33121)
- Defined 14-PDIP package variant (karşılaştırma:MC33121)
- Subsystem-level supervision (karşılaştırma:MC33121)
Tasarım Notları
Keep the MC33121P's analog and digital grounding domains consistent with the manufacturer reference layout. Transmit and receive signals are referenced to analog ground, while hookswitch, fault, and power-down signals use digital ground. Avoid routing subscriber-loop current or codec switching currents through the analog return path. Because the verified excerpts do not provide the individual pin assignments or lead dimensions, confirm both against the manufacturer package drawing before releasing artwork.
Do not assume that another SLIC in a 14-pin DIP is a drop-in replacement. A valid substitute must match pin numbering and every functional connection, including battery feed, loop termination, transmit, receive, transhybrid gain controls, hookswitch, fault outputs, and power-down. The supplied cross-reference results contain no verified equivalent, so an existing PCB should be reworked or the replacement validated against the complete datasheet before substitution.
The MC33121P includes a power-down input for local shutdown, but the verified excerpts do not state its supply-voltage range, quiescent current, or logic thresholds. Do not infer power specifications from the low-voltage SLIC description. Verify operating and absolute maximum ratings, logic levels, and power sequencing in the manufacturer datasheet, particularly when the device shares a board with codecs, filters, or digital processors.
Place the line-facing network and MC33121P in the same protected analog section of the PCB, and keep codec and digital control routing away from sensitive subscriber-loop nodes. Use the manufacturer's reference circuit for all adjustable-gain components and loop termination because the verified information does not provide their values. The documented 58 dB minimum longitudinal balance is meaningful only if component tolerances, grounding, and board leakage are controlled as intended by the reference design.
Uyumluluk Bilgisi
The supplied verified excerpts do not provide RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive-qualification statements. No compliance claim can therefore be verified. AEC-Q100 is marked not_applicable because this product is a legacy telecommunications interface rather than an automotive-qualified device identified in the source data.
