These boxes were obtained from a Corporate TV studio, and most of them show few signs of any use. These KB-111s are in P-Boxes -- "Clear-Com P-Box, a sturdy, lightweight aluminum enclosure with a sloped front, walnut sides, and carry strap. Provides 3-pin input and extension connectors".
Here are some of the features from Clearcom:
The KB-111A is a high-quality remote speaker station that allows talking and/or listening on one of any two channels in a Clear-Com system (not both simultaneonsly).
Compatible with all Clear-Com intercoms, this station features excellent speech intelligibility in high- and low-noise environments. The wide frequency response speaker delivers crisp sound quality at levels high enough to be heard in the noisiest surroundings.
The KB-111A operates with a carbon headset, dynamic headset, or a telephone-style handset. It drives a standard Clear-Com headset to levels greater than 110 dB SPL. The station’s speaker can be turned off when private conversation via the headset is desired; alternately, a mic on/off switch is provided to to let the station function as a “listen only” or “remote page” station.
The station contains a recessed sidetone control, which allows the operator to vary the level of his/her own voice as heard in the headset/speaker. Sidetone control also suppresses acoustic feedback when the mic and speaker at that station are on simultaneously.
The KB-111A features Visual Call Signaling; the Call button allows you to attract the attention of operators who have removed their headsets or turned off their speakers. The Call lamp illuminates when another operator presses the Call button.
The station is designed to be custom-mounted. It can be installed on a wall or console, or inside a standard 6" x 8" NEMA electrical box. Clear-Com provides optional portable boxes (see accessories).
Standard mic cable connects the KB-111A to the intercom system. The station provides a clearly labelled screw-terminal block for interconnection behind the front panel.
High-impedence current sourcing and low current drain allow as many as 20 KB-111A stations to be connected along one mile of wire with no significant loss of signal level or audio quality.
The circuit design virtually eliminates all hum and noise pick-up from SCR dimmer and AC power sources.
KB-111A & KB-112 SPECIFICATIONS
AMPLIFIER DESIGN Solid-state, integrated-circuit amplifiers which include a mic preamp, headset/speaker power amplifier and signaling circuitry. Current limited with short-circuit and reverse-polarity protection.
MIC PREAMPLIFIER Frequency Response: 200 Hz - 12 kHz with contoured response to enhance voice intelligibility.
KB-111A Mic Input: 200 ½ Mic Preamp Gain: 37 dB KB-112 Mic Type: electret Gain: adjustable 11 dB
HEADPHONE AMPLIFIER Frequency Response: 100 Hz - 18 kHz, ±2 dB Headset Impedance: 8 - 2,000 ½ Output Level: +20 dB @ 600 ½ Amp Gain: 37dB Remote Speaker Stations
SPEAKER AMPLIFIER Speaker Type: 3" square Power Output: 2 watts Frequency Response: 100 Hz - l5 kHz Distortion: 0.5% THD at 1 kHz Speaker Level: 98 dB SPL at 3 feet
GENERAL Signal-to-Noise: 75 dB Line-to-Speaker Gain: 30.5 dB Headset Level: >110 dB SPL with standard ClearCom headsets Line Level: -15 dBv nom*, 0 dBv max Sidetone Adjustment: 35 dB null to full on Signaling Voltage: 11 volts DC on audio line Call Light Sensitivity: 4 volts Station Bridging Impedance: >15 k½ KB-111A & KB-112
PROGRAM INPUT Impedance: 500 k½ Level: .7v for max output
POWER REQUIREMENTS 20 mA quiescent, 60 mA average talk or signaling. 150 mA maximum load. Voltage Range: 12 - 32 volts, 28 volts nominal
CONNECTORS Headset: 4-pin male XLR Line: 5-screw terminal block
DIMENSIONS: 8.6" x 6.5" x 1.43" (218mm x 165mm x 36mm)
WEIGHT: 1.6 lbs. (.73kg) Specifications subject to change without notice *0 dBv is referenced to 0.775 volts rms.