Sigtronics SPE-2 - Manual

Transcom is a voice actuated aircraft intercom with the capability
for transmitting through the aircraft radio by the mere push of a
button. It was designed for simplicity of use. Three controls are
provided on the front panel. (See Figure 1)
POWER SWITCH — Turns unit on and off.
VOLUME CONTROL — Controls the intercom volume. (The radio
volume is controlled conventionally.)
SQUELCH CONTROL — Controls the threshold of amplifier
turn-on. This control is normally used to adjust for variations in
background noise found in different aircraft.
Two Microphone Input Jacks, labeled MIKE, are provided. They
accept the standard aircraft mike plugs (i.e. carbon or amplified
dynamic microphone.)
Two Output Jacks are provided, labeled HDPH which accept the
standard .250” aircraft headphone plug.
Two jacks are provided on the panel, labeled XMIT SW which
accept the standard aircraft .206” mike plugs: found on aircraft
push-to-talk switches. These are normally not used in the
Permanent TRANSCOM, since provisions are made for hard
wiring the push-to-talk functions to the aircraft. However, they may
be used as an option with portable aircraft push-to-talk switches.
Transmitting from both positions is possible on a one-at-a-time
basis. Each position disables the other while transmitting.
OPERATING INSTRUCTIONS
After the intercom is installed per the instructions above, it is
ready for use. Figure 2 illustrates the connections between the
TRANSCOM and headsets. In addition, push-to-talk switches are
shown in Figure 2 with dashed line for reference only. Portable
push-to-talk switches may be plugged in as shown, if it is not
desired to connect the orange and yellow wires as shown in
Fig.3.
STEP 1 — INTERCOM MODE
A. Turn the power switch on.
B. Set the volume control to a low level.
C. Adjust the squelch control clockwise until background noise
increases or the voice is heard by speaking into mike. Rotate
the squelch counterclockwise until noise diminishes. Then
make small adjustments until the voice triggers the unit on
satisfactorily. Small adjustments may be necessary if the
aircraft background noise changes significantly, such as from
idle to full power.
SIGTRONICS “TRANSCOM” INSTALLATION AND OPERATING INSTRUCTIONS (PERMANENT)
STEP 2 — TRANSMIT MODE
When ready to transmit, depress the Transmit Switch and your
voice is automatically transmitted via the aircraft radio.
STEP 3 — RADIO MONITORING
When the unit is connected as shown, radio monitoring is
automatic. The radio monitor circuit is always active, even with
the TRANSCOM Power Switch in the OFF position.
HELPFUL HINTS
Position the boom mike in close proximity to the mouth, as is the
practice with a hand held mike, for best results.
Maintain minimum acceptable volume when using TRANSCOM
– particularly in low noise environments.
A fuse is located within the unit and may be replaced by a qualified
person should the need arise.
The hand held mike may be left plugged into the aircraft mike input
jack and used conventionally. However, the TRANSCOM must
be switched off during transmitting. Radio reception will continue
through the headphone, even with TRANSCOM switched off.
When transmitting the intercom is automatically switched OFF and
your voice is heard via the aircraft radio sidetone return. In cases
where there is no sidetone return, nothing will be heard.
The push-to-talk switch circuit must have less than 5 ohms
resistance for satisfactory operation.
FIGURE 1
FIGURE 2
SIGTRONICS TRANSCOM CONNECTION SCHEMATIC