Issue 1, October 1997 Model 770 User Guide
Page 42 Studio Technologies, Inc.
Model 770
IFB Section
General Audio Parameters:
Audio Switching and Muting: clickless using
special ramping analog switches
Frequency Response: 20Hz-20kHz, ±0.5dB,
IFB line in/IFB line out
Distortion (THD+N): 0.04%, measured at 1kHz,
+4dBu input to IFB line in/IFB line out
S/N Ratio: 71dB, referenced to +4dBu to IFB line
in/IFB line out
Interrupt Audio Limiter/Compressor: studio
quality, dual slope
Gooseneck Microphone Limiter/Compressor:
studio quality, dual slope
Line Inputs: 4
Type: electronically balanced, direct-coupled,
compatible with balanced or unbalanced signals
Impedance: 24k ohms
Common Mode Rejection Ratio: 80dB @ 60Hz,
70dB @ 40kHz, typical
Nominal Level: +4dBu, adjustable over ±8dB
Voice Operated (VOX) Interrupt Function:
Detection Bandpass: 400 to 1400Hz, nominal
Detect Time: less than 1mSec
Detect Level: 18dB below nominal
IFB Line Output:
Type: balanced, transformer-coupled, intended
to drive balanced or unbalanced loads of 2k
ohms or greater
Source Impedance: 170 ohms, nominal
Nominal Level: +4dBu
Maximum Level: +21dBu into 10k ohms
IFB Intercom Link Out: allows direct connection
to RTS/Telex intercom buses
Output Type: current source
Output Impedance: 10k ohms, nominal
Output Level: 18dBu when connected to 200
ohm load
Talent Amplifier Output:
Application: provides power and audio signals
for up to four Model 32 or Model 33 Talent Ampli-
fiers. The output connector (3-pin XLR-type, male)
has common on pin 1, +22Vdc modulated with
IFB audio (10dBu nominal) on pin 2, and select-
able audio source (10dBu nominal) on pin 3.
Telco Interface:
Application: selectable for compatibility with
telephone line (wet) or standard audio (dry)
signals
Impedance: 600 ohms
Receive Audio Level: 15dBu, nominal, adjust-
able over ±8dB range
Send Audio Level: 6dBu, nominal
Telephone Line:
Compatibility: 2-wire, loop start, 10mA loop
current minimum
Ring Detection: 40-150Vrms, 18-68Hz, ringer
equivalence 1.0B
Auto Answer: after detection of two complete
ring cycles (can be disabled)
Disconnect: manual using front-panel switch;
automatic after detection of break in loop current
Overcurrent Protect: solid-state, automatic reset
IFB Monitor Output:
Type: electronically balanced, capacitor-coupled,
intended to drive balanced or unbalanced loads
of 600 ohms or greater
Source Impedance: 50 ohms, nominal
Nominal Level: 4dBu, with monitor level control
@ 100%
Maximum Level: +19dBu into 10k ohms,
+18dBu into 600 ohms
Monitor Section
External Monitor Inputs: 2, monaural
Type: electronically balanced, direct-coupled,
compatible with balanced or unbalanced signals
Impedance: 24k ohms
Common Mode Rejection Ratio: 80dB @ 60Hz,
70dB @ 40kHz, typical
Nominal Level: +4dBu
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