- Transmitter Type: ET - Carbon Compatible Electret element designed into a amplified circuit to act as a Carbon without variations - Output Level: -23 dBV - Output Impedance: 20 - Output Minimum (-20 dBV drive): 96 dBSPL - Input Impedance: 150 Ohm - Amplitude Limiting: 124 dBSPL - Receive distortion: less than 5% - Compatible with hearing aids - PTT handsets do not require a hook switch in cradle - G-Style / 500-Style Round Receiver & Transmitter Ends - Connector: 4 conductor modular jack (RJ22) - Compatible with Cortelco 2500 and 2554 series telephones