Crystal Vision
Installation
5.2 Signal earthing
Audio inputs are designed to have floating ‘signal low’ connections for cable screens,
with internal RC networks connected between cable screens and chassis ground. This
helps reduce the risk of high earth currents when AC power is induced into the cable, or
when an offset voltage exists between the product chassis and the local signal source
ground or chassis.
The internal RC network components fitted in the ADCA412 PCB are as follows:
Component
Signal low (screen)
Chassis ground
1µF capacitor
IP-1LO / IP-2LO / IP-3LO / IP-
PCB GND
10K ohm resistor
IP-1LO / IP-2LO / IP-3LO / IP-
PCB GND
Note:
Video and audio output cable screens are normally hard-wired directly to local chassis
ground.
5.3 Using GPIs
GPI input assignments
The ADAC412 supports four GPI input lines, which are assigned functions as follows:
GPI
Effect when GPI input is asserted low
GP1-1
Changes dual input circuits to just one stereo audio input feeding all
AES outputs.
GP1-2
Swaps stereo audio 1 input circuit with stereo audio 2 input circuit to
exchange the two AES output signal contents one with the other.
GP1-3
Changes AES Reference input circuit only from Xtal Mode to Auto
Mode.
GP1-4
Changes AES Reference input or Word Clock input to VIDEO Syncs
Reference Input, if present. Ignored if INTERNAL free run clock has
The GPI inputs override the switch settings and remote control settings, unless the
existing setting selects the same operation, as the GPI input would have done, in which
case there is no change of operation.
Each input looks like a TTL/CMOS input and has a 10k pull up to +5V, and is ‘asserted’
by pulling down to 0v.
GPI output assignments (alarms)
The ADAC412 supports two GPI output lines, which are assigned functions as follows:
GPI
Alarms are active when asserted low
GP1-5
AES 1 Alarm - loss of input and silence detected
GP1-6
AES 2 Alarm - loss of input and silence detected
Normally loss of Selected Reference Input will assert both GPO 5 and GPO 6 low and
any sustained silence on channel 1 will assert GPO 5 low and sustained silence on
channel 2 will assert GPO 6 low.
ADCA412 User Manual R2.1
31
30 October 2018
