How the Companion Mics System Works
The Companion Mics system establishes a direct communication line between the Talkers’ microphones and the Listener’s receiver, which bypasses the noise and reverberation of the local acoustic environment. The wireless technology used in the Companion Mics system is similar to that used by digital cordless phones and other digital users of the 2.4 GHz band.
Rather than using a single frequency, where a competing signal might interfere, a frequency-hopping technique is used. By jumping quickly from frequency to frequency in a pseudo-random manner among 79 frequencies, the chance of interference from microwave ovens, other Companion Mics systems or other users of 2.4 GHz is minimized, so that 10 or more sets can operate with little audible interference even if they are all in the same room.
When the units are first turned on, the Listener Unit starts its repeating sequence of frequency hops while each Talker Unit waits, tuned to one or another of those frequencies, until it receives a transmission containing the identification code from the Listener Unit. The units then lock together, jumping from frequency to frequency. This process is repeated until all Talker Units lock on.
Once all units are in communication with each other, the LED lights stop blinking and the Talkers are heard by the Listener. From then on, each Talker Unit is in constant communication with the Listener Unit. The “lock up” sequence normally takes less than 8 seconds, but—rarely—may take 20-30 seconds if heavy interference is present.
A master volume control on the Listener Unit adjusts microphone gain on all units simultaneously. Each individual Talker Unit has an independent volume control to fine tune an individual microphone gain to accommodate loud or soft talkers.
Specifications
Operating Distance
Under line-of-sight conditions out in the open, the units may operate over a distance of 150 feet or more. Indoors, where there are reflections, the units should maintain communication over a distance of 15 to 20 feet even if the Listener and Talkers occasionally turn their backs to each other.
Technical Specifications
Power Consumption: 50-65 mA at nominal voltage
Battery Life: 10-13 hours
Charging Time: Typically 2-3 hours from “empty”
Environmental Performance: Operating: -10 to +45 °C
Charging: 0 to +35 °C
Storage: -10 to +45 °C
Radio Performance: 20 meters (66 feet) min in free space
Audio Performance
Frequency Bandwidth: 8 kHz (7 kHz for two-way system)
Acoustic Insertion Gain at Startup (preset volume): 20 dB gain
Volume Control Gain Range: 4 dB to 66 dB*
Maximum output: 119 dB SPL*
Total Harmonic Distortion: < 2%
End-to-end Delay: 22-32 msec (low-interference environments);
30-40 msec (four microphone systems)
Earphone Minimum Output Impedance: 10 Ohms
Telecoil Minimum Output Impedance: 10 Ohms
Max Voltage Swing at Receiver Output: 1.95-2.00 Vpp
Antenna: Internal
Microphone: Noise-canceling electret condenser
*Notes:
- Gain and output depend on the earphone that is used. These specifications apply when the Companion Mics system is used with the supplied 6i Isolator™ earphones.
- Maximum output is measured into a 2cc coupler with 90 dB SPL input.
- Technical note for audiologists: When a hearing aid microphone is moved from the ear of the listener to a position a few inches below the talker’s mouth, an increase of 16-20 dB SPL is obtained. Insertion gain refers to the increase in ear canal SPL provided by the Companion Mics system compared to listening directly to a talker one meter in front of the listener.
