TTC-121

Overview

The Tamura TTC-121 is a discontinued through-hole audio transformer designed for voice and modem applications. It features a primary impedance of 600 Ohms and a secondary configuration of 600 Ohms with a center tap (300/300 Ohms). The device operates within a frequency range of 300Hz to 3.5kHz, maintaining a frequency response of ±0.7dB. Key electrical specifications include an insertion loss of 1.1dB typical at 1kHz, return loss of 18dB standard, and isolation voltage of 1500VRMS for one minute. DC resistance is 74 Ohms on the primary side and 64 Ohms on the secondary side.

Feature Summary

• Provides galvanic isolation between voice or modem circuits via high-voltage insulation capabilities.
• Supports balanced line interfacing with a center-tapped secondary winding configuration.
• Engineered for stable signal transmission across standard telephony frequency bands.

Applications

• Voice communication systems requiring line isolation.
• Modem interface circuits for signal conditioning.
• Telephony equipment utilizing 600-ohm balanced lines.

Procurement Notes

This component has been officially declared obsolete by the manufacturer and is no longer in production. Sourcing new units from original channels is not possible. Procurement efforts must focus on identifying verified direct replacement parts that match the required electrical parameters and physical footprint. Verify compatibility thoroughly before integration into designs.

Selection Notes

Designers should prioritize components with matching 600-ohm impedance ratios and similar frequency response characteristics. Ensure the replacement supports the necessary isolation voltage and physical mounting style. Since this part is end-of-life, selecting a modern equivalent with comparable insertion loss and return loss specifications is critical for maintaining system performance in voice and data transmission applications.

Part Context

The TTC-121 belongs to Tamura's series of audio and signal transformers, historically utilized in telecommunications infrastructure. As a legacy component, it represents older generation magnetics technology. Its discontinuation reflects industry shifts toward surface-mount technologies and newer integrated solutions, necessitating careful evaluation of alternative discrete components for existing maintenance or replication projects.

Replacement Considerations

The TY-306P from Triad Magnetics is documented as a direct substitute. This alternative offers compatible functionality for voice and modem transformer applications. Engineers should verify pinout alignment and mechanical dimensions to ensure seamless integration without PCB redesign requirements.

FAQ

What is the current manufacturing status of the TTC-121?

The TTC-121 is classified as obsolete and is no longer manufactured by Tamura.

Does the secondary winding have a center tap?

Yes, the secondary side is configured as 600 Ohms with a center tap, effectively providing two 300 Ohm sections.