3
- The voice is clear when the call is made, the sound is loud, and there is no feedback whistling.
1.2. Technical Parameter
- Ringing Level: 70dB
（
A
）
- Pulse dialing
The interrupt ratio of the dial pulse is 1.6±0.2 : 1.0
Dial pulse speed: 10±1 times/second
Dual Tone Multi-Frequency (DTMF) dialing:
- Frequency offset: ≤1.5%;
- Low frequency group level: -9±3dB;
- High frequency group level: -7±3dB;
- High and low level differences in the frequency combination: 2±1dB;
- Total distortion such as harmonics is at least 20dB lower than the fundamental level
- Call transmission index: SLR
≤
12, RLR
≤
-1, STMR
≥
10,
- Output impedance: 600Ω
- Electroacoustic characteristics:
Send loudness rating ≥+2dB ≤+12dB
Accept the loudness rating ≥-8dB ≤-1dB
Lateral masking rating ≥+3dB ≥+10dB
2. Installation method
Reserve a suitable space in the wall to be installed, insert it into the wall and fix it with stainless steel screws.