SEA 235, Operator'S Manual

Page: 101 / 104

REAR PANEL
96
REAR PANEL CONNECTIONS
(cont.)
Pin 6 - Internal switch ON allows unsquelched audio to be present at this pin.
Equivalent to LLAF on Accessory connector P3. (SW1-2).
Pin 7
- Internal switch ON allows transmit audio to enter the radio. Equivalent
to TXAF on Accessory connector P3. (SW1-3).
Pin 8 - Internal switch ON allows 13.6 volts to be present when the radio is
turned on. (SW1-6). DO NOT EXCEED 3 AMPS.
Pin 9 - Internal switch ON supplies extra ground pin. (SW1-5).
NOTE
:
The SEA 235 is shipped with internal switches in the OFF position. This will
allow a general purpose RS232 port on Pins 3,4 and 5 and removes all other
connections to the remaining DB-9 pins. It is possible to damage any external
accessories, the SEA 235 or both when the switches are set incorrectly!
PARALLEL INTERFACE - P3 :
Use for interconnecting additional equipment requiring accesses to the radio
transmit and receive circuitry along with tuner connections.
GND - (Pins 1 and 7) Provides access to the negative side (ground) of the
primary supply. Also common to chassis.
PTT - (Pin 2) Applying a ground potential to this connection activates the
transmitter.
MIC - (Pin 3) Auxiliary input for a dynamic microphone.
HANDSET
- (Pin 4) Handset receiver audio. 600 ohms.
AF - (Pin 5) AC coupled output of the audio power amplifier. Speaker
impedance required is 3.2 ohms or greater.
SPKR (Pin 6) Internal speaker input. A jumper to the AF terminal is required
to operate the internal speaker.
13.6S
(Pin 8) 13.6 volts, switched. Normally used to power an external
antenna tuner such as the SEA 1635 or SEA 1612C.
DO NOT EXCEED 3
AMPS
. Fused with a 5 amp fuse located on the PA/Filter board.
TND (Pin 9) Input signal from the tuner to indicate a “matched” antenna.
Grounding this line will cause the “TND” indicator to display.
DMD TUNE (Pin 10) This output terminal provides the connection to
operate the “DEMAND TUNE” function in the SEA 1635 and SEA 1612C.
LLAF (Pin 11) Low level receiver audio output (unsquelched). Configured
for unbalanced 300 ohm lines, nominal output level is 1 volt peak-to-peak.
TXAF (Pin 12) Input for an alternative transmitter audio source such as a
MODEM. Configured for unbalanced 600 ohm lines. Nominal input level for
full modulation is 1 volt peak-to-peak.