Biamp AUTOTWO - Manual (Page 6)

4
LOGIC OUTPUTS
The autoTWO provides eight logic outputs on a rear panel 9-pin Subminiature D (male) connector. Logic Outputs can be used to control
external switching circuits for speakers, cameras, indicators, etc. The autoTWO Logic Outputs are most often used, in conjunction with
external relays, to turn off specific speakers when nearby microphones are active (reducing feedback problems). For example, if a speaker
is located directly above microphone #1, the Logic Output for Channel 1 of the autoTWO can be used to turn off that speaker relay when
microphone #1 is active (see diagram on next page). The Logic Outputs can also be combined (wired in parallel) to control a single circuit.
For example, a speaker relay could be turned off when either microphone #1 or microphone #2 is active. In addition to speaker relays, the
autoTWO Logic Outputs may be used to control external indicator lights (see diagram on next page). Another common application for
Logic Outputs is to control video cameras. Different cameras could be activated depending upon which microphone (or group of
microphones) is currently active. Cameras can be selected using a video switcher and/or ‘pan/tilt/zoom’ camera presets. The Logic
Outputs may also be used in conjunction with the Expansion jack (pin 6 & pin 3) to perform ‘automatic priority’, which allows all other
channels to be muted whenever the Channel 1 microphone is active (see diagram on next page). The Logic Output (pin 1) & ground (pin
9) terminals for the Channel 1 ‘priority’ microphone are wired to pin 6 & pin 3 respectively of the Expansion jack. A switch or contact-
closure may instead be used, for manual priority override.
The autoTWO Logic Outputs are ‘open collector’ outputs. Each Logic Output is an NPN transistor with the collector being the output and
the emitter being ground (see diagram on next page). When a Logic Output is turned on, the transistor provides a path for DC current to
flow. The Logic Outputs do not provide any voltage or current. They act only as switches (with a common ground return). To activate
external relays, an external power supply must be used (see diagram on next page). The Logic Output transistors are rated up to a
maximum of 24 VDC and 50 mA per output (24 volt relay coils maximum). However, +12 Volts DC is sufficient power for most
applications. When using the Logic Outputs to control relays, protection diodes must be used to suppress high voltage transients that are
generated when the relays turn off (see diagram on next page). Any of the 1N4004 family of diodes (1N4001, 1N4002, 1N4003, 1N4004,
1N4005, 1N4006, 1N4007, or equivalent) will provide proper protection. When a Logic Output goes on, the associated relay may be wired
to perform on, off, or ’A/B’ switching functions. To use logic ‘on’ to turn on (or activate) a device, wire across the ‘normally open’ relay
contacts, in series with the device (or control voltage source). To use logic ‘on’ to select between ‘A’ or ‘B’ signals (inputs or outputs), wire
one signal to the ‘normally closed’ relay terminal and the other signal to the ‘normally open’ relay terminal, with the common relay terminal
providing the feed (input or output).
The 9-pin Sub-D connector used for the autoTWO Logic Outputs is the same type of connector used for RS-232 communications ports on
IBM compatible computers. A cable may be created by simply wiring to the proper pins of a female 9-pin Sub-D cable-end connector.
logic out pin number
channel 1
channel 2
channel 3
channel 4
channel 5 pin #1
pin #2
pin #3
pin #4
pin #5
pin #6
pin #7
pin #8
pin #9
channel 6
channel 7
channel 8
ground
9-pin cable-end
5
9 8
7 6
1
2
3
4
logic outputs
1 2 3 4 5
6 7 8 9