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Knowledge Base > Discontinued Products > TI-101 Telephone Interface

The announcer's voice sounds "hollow" when we use the TI-101 Telephone Interface.

Under normal conditions you will notice leakage of the host audio into the caller audio. This is the nature of analog hybrids. When properly adjusted, the caller’s audio level should be 3 to 6dB higher than the host audio leakage. Since this leakage is out of phase with the source audio a change in tonal quality is normal.

Where can I find a Data Sheet for the TI-101 Telephone Interface?

TI-101 Telephone Interface has hum in the caller audio

The signal to noise performance of the TI-101 can be improved 15 dB by relocating the power transformer. If your power transformer is mounted on the bottom of the chassis its field induces hum into the caller output transformer. Remounting the power transformer to the side of the chassis corrects the problem. The details are in the TI-101 Service Notes.

TI-101 Telephone Interface won't hold the phone line open.

It was not designed to. The TI-101 requires a telephone holding coil wired in parallel with the telephone input connections. Use a Microtran T4415. It is a choke rated at 2.0 Henrys @ 60 mA, with a DC resistance of 180 ohms. You will also need to add a switch in series with the holding coil in order to drop the line when you are ready to release the it.

Will the TI-101 Telephone Interface work with an electronic telephone system?

The design of the TI-101 limits its dependable use to standard central office lines. Installing an analog adapter or analog circuit card in the system might be a solution. It is your only choice if the telephone system digitizes the audio. Using this mode of operation, install the hybrid and a single line telephone on the analog extension. Answer incoming calls on the regular system and transfer them to the analog extension.

To assure that you get the right equipment, tell your phone installer that you want a fax machine on that extension. If a fax machine will operate on a line, a telephone hybrid will also. Your phone installer will not understand what you need if you talk to him about a “phone hybrid”. He will understand the requirements for a fax machine.

Where can I find schematics for the TI-101 Telephone Interface?

How do I adjust the null on the TI-101 Telephone Interface?

Place an outside call to someone. Once on the line, have them put the telephone handset down in a quiet place. Connect pink noise, white noise or simply music to the HOST INPUT. Listen, or meter, the CALLER OUTPUT and adjust the COARSE NULL for a minimum of the noise or music in the caller output. Repeat the adjustment for both the LF (low frequency) and HF (high frequency) nulls.

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