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TYPE 120 DTMF
CONTROL SYSTEM
The Amcro
Technology TYPE 120 DTMF CONTROL SYSTEM is intended for
the remote control of equipment, and/or remote telemetry
and monitoring of equipment, by means of an audio tie-line
or radio link. It is capable of being used with 2-wire or
4-wire audio cabling, and can operate as a one-way system,
or as a bi-directional system with control or data
information passing both ways (duplex mode). The use of
DTMF tones means that the control circuit may be shared
with voice communications with minimal interaction. It
also makes control possible over poor quality audio
circuits.
APPLICATIONS
 This system was originally designed for
remote control of a broadcast camera at a remote and
unattended (except for the presenter!) news studio. It
directly switches power to a pan-and-tilt head, and also
controls zoom, focus and white-balance-enable on the
camera. In the studio, an on-air light and a warning
buzzer are provided, together with local VTR control. The
camera is operated from the Master Control suite at the
TV Station's main studio centre. Control is by means of
DTMF tones through an audio tie-line. Provision is also
made for dial-in from a Touch-Tone telephone in special
circumstances. The pan-and-tilt DTMF tone assignments are
mapped to their locations on the phone keypad, i.e. 2 for
up, 8 for down, 4 for left and 6 for right. The control
outputs are in the form of closing GPI/O relay contacts,
and are a mixture of momentary, toggle, and "on
demand" (i.e. asserted only whilst the command tones
are present). The system readily lends itself to other
applications, and is now described in more detail.
HARDWARE
CONFIGURATION
The system is
designed around a number of general purpose extended
Eurocard (100 x 220mm) modules, which may be configured
for a particular application. These are:
COMMS BOARD
This is a full-duplex
capable DTMF transceiver, with line driving/receiving
capability. It has full BT specification line DC
isolation, and over-voltage surge protection.
CONTROL BOARD
This is the heart
of the system, and forms the interface between the COMMS
board and the RELAY boards. It also has a full
specification RS-232 serial port, configurable from 50
Baud to 19.2K Baud data rate. The board houses a
microcontroller system, with the program contained in
EPROM. Non-volatile RAM storage of data is possible. The
operating firmware would normally be tailored for the
required application.
RELAY BOARDS
Type 1 & 2
These provide the
control switching functions. Relays were chosen as they
provide fully DC-isolated volt-free control. RELAY BOARD
1 has 12 change-over functions with 1 Amp max. rated
contacts, and is intended for low current control
switching. RELAY BOARD 2 has 5 change-over functions,
with 10 Amp max rated contacts, for directly switching
low-voltage power controlled systems, such as remote pan
& tilt heads.
PACKAGING
The modules are
normally housed in a 1U (3 modules+PSU) or 3U (16 Modules+PSU)
rack frame. The precise module configuration is flexible,
dependent upon the application.
© Amcro Technology Ltd. 2002
Amcro Technology
Ltd.
1 Lambourne Way
Thruxton
Andover
SP11 8NE UK
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