Transducer Electronics Circuit Description; A-3.1 Multiplexer; A-3.2 Transmit Path; A-3.3 Receive Path - Teledyne ADFM Pro20 Technical Manual

signal width a minimum duration of 400 ms. The Modem must be able to
send a Break signal with a minimum duration of 300 ms.
The RS-232 serial data interface is located at the front panel of the ADFM.
It is intended for local operation of the ADFM. This single ended interface
allows maximum baud rate of 19.2 k-Baud over a distance of 15 meters.
Longer distances may be possible at lower data rates. Handshake lines are
not available.
The front panel LCD displays the ADFM operating status. Self-test results
are indicated as well.
A-3

Transducer Electronics Circuit Description

The following description refers to Figure A-29. The legends used are
spelled out more precisely in Table A-210.
A-3.1 Multiplexer
Prior to a ping, the transducer micro controller (XDCR-CTL) selects a
beam via a solid state transmit and receive multiplexer, which is part of the
transmit/receive switch (T/R-Switch), and the pre-amplifier (PA) respec-
tive. The specific beam number the XDCR-CTL selects is set up by the
ADFM's Electronics Unit via a half duplex serial communication port
(SDIN, and SDOUT) between the Electronics Unit and the transducer con-
troller.
A-3.2 Transmit Path
The transmit signal, generated by the ADFM's Timing Generator, arrives at
the transducer electronics terminals labeled XMT. It passes through the
transmit coupling transformer (XMT), which provides isolation and imped-
ance matching. The signal then is mutilplexed to one of five beams via the
prior selected T/R-Switch, which also isolates and protects the pre-
amplifier (PA) during transmit. At the end of transmit the transmit multi-
plexer is deselected, but the appropriate PA remains selected.
A-3.3 Receive Path
The echo from the water is received through the same selected transducer,
band-pass filtered, and amplified by the prior selected pre-amplifier (please
notice, only one pre-amplifier is selected at any given time). The PA's out-
put signal is buffered by a buffer amplifier (BUFF) that is common to all
five channels. The buffer amplifier provides decoupling and impedance
matching. The signal eventually is converted to a differential signal by a
wide-band signal transformer, and is available at the transducer terminals,
labeled RCV-SIG. After the signal is received, the transducer controller de-
selects the pre-amplifier.
ADFM Technical Manual (January 2000)
ADFM System Overview
page A-5