Specifications
Section N
External Interface (A23)
N.1 Introduction
This section describes the External Interface board. Topics in-
clude function, location, detailed circuit description, trou-
bleshooting, and removal/replacement.
NOTE: Parts List for this board is covered in Section VII.
N.2 Function
The External Interface board receives Remote Control Inputs and
provides Remote Status and Metering Outputs. It also contains the
Audio Input Connections and the External Interlock circuit.
N.3 Location
The External Interface Board is located behind the center front
door.(SEE VIEW 12)
N.4 Detailed Circuit Description
Refer to the External Interface Schematic (839-7930-017) and to
the External Interface Chart (839-7930-162) for the following
discussion.
NOTE
Several circuits on the External Interface board have been re-
served for use only when in a combined transmitter operation. If
any part of the schematic is blocked in using dashed lines, these
components may not have been installed for single transmitter
operation. Their use in combined operation is discussed in the
manual for combined transmitters.
N.4.1 Remote Status Outputs
Several fault indications, as well as LOW, MEDIUM, HIGH, and
OFF transmitter modes can be monitored using the status out-
puts. J7 supplies inputs from the Controller to the status output
drivers U1, U2, and U6, except for the RF Mute Status.
The operation of all the output driversare the same.These drivers
provide isolation between the Controller and the external remote
control circuits. When the input to an output driver is pulled low
by the Controller, the driver’s output also goes low.
This output can be used to illuminate an LED or turn on an opto-
isolated status input to a remote control system. The output can
also be used to activate a relay, however current through the
output driver and the output resistor should be limited to 100 mA.
The voltage must be limited to a maximum of +15 VDC.
Examples of TTL logic and Relay outputs are shown in Figure N-1.
Should transient voltages develop on the remote status lines,
protection diodes on the output of each driver will clamp the
output at +15.6 VDC or -0.6 VDC.
A regulated +15 VDC at 100 mA is provided at J4-18 for use
with the Remote Status Outputs. If a larger current supply is
needed, an external power supply should be used.
Two drivers have jumpers on their input. The Interlock Open and
the LV Supply Fault status driverswill have jumpers P25 and P26
positioned from 1-2 for single transmitter operation.
The Transmitter Select Switch S1 is also provided for combined
transmitter operation. For single transmitter operation S1 is
jumpered to the Master position and therefore supplies a Switch
Ground for U1 and U6.
A second output for LOW, MEDIUM, HIGH, and OFF is provided
for combined transmitter operation through J3-1 thru 4.
N.4.2
Remote Control Inputs
All Remote Control functions are accomplished through optically
isolated control inputs using opto-isolators U3, U4 and U5. All inputs
are programmable to accept either high or low control inputs.
The Remote Control Inputs are enabled by an active high from
the Controller board at J7-9. This voltage will turn on transistor
Q1, which provides a ground for the emitter of each opto-isolator.
The only exception is the RF Mute Control. Remote Control
Active status is provided by Q5.
A jumper plug is provided on the input of each opto-isolator to
allow programming for high or low control logic.
NOTE
All inputs must be configured the same way.
With the input jumpers P1 thru P11 positioned as shownin Figure
N-2, a ground applied to the control input will activate the control
function.
With the input jumpers P1 thru P11 positioned as shownin Figure
N-3, +5 VDC applied to the control input will activate the control
function.
Figures N-4 and N-5 show examples of remote control from relay
contact or TTL logic level inputs.
The Remote Control Inputs are connected to 37 pin “D” connec-
tor J6. A terminal strip adapter is provided for use with the “D”
connector.
A regulated +5 VDC is provided at J6-18 for use with the Remote
Control Inputs. If an external power supply is used it should be
limited to a maximum of +15 VDC.
Parallel inputs are provided for combined transmitter operation
via J5 for LOW, MEDIUM, HIGH, OFF and RF MUTE.
N.4.3
Metering Outputs
N.4.3.1 Remote Metering
Operational amplifiers U14, U15 and U16 provide Remote Me-
tering for six transmitter parameters.
888-2339-002 N-1
WARNING: Disconnect primary power prior to servicing.