TECHNISONIC INDUSTRIES LIMITED
TDAP-611 Operating Instructions
TiL 15RE553 Rev. B
3
1.5
SYSTEM LIMITATIONS
A summary of the relevant system limitations is given below.
1.5.1 POWER LIMITATIONS
With Standard Set-up, which consists of seven headsets connected, a power output of not less
than 250 mW is delivered per headset (as represented by 150 ohms).
Nominal microphone input: 250 mV
rms
; Nominal Communications/Navigational Input: 2.5 V
rms
.
1.5.2 FREQUENCY RESPONSE LIMITATIONS
In accordance with the provisions made in RTCA/DO-214 Sections 2.8.1 and 1.5.1, the
communications transmit out and receiver channels (communications and navigational) possess
an effective bandwidth of 300 Hz – 3000 Hz with a maximum amplitude variation of 3 dB within
the frequency range.
1.5.3 CROSSTALK LIMITATIONS
To ensure that the crosstalk specifications are in accordance with the applicable sections of
DO-214, it is essential that
1) Manufacturer’s maximum microphone input voltage of -4.7 dBu must not be
exceeded in order to avoid jeopardising input to microphone output crosstalk results,
particularly at the low frequency end.
2) In the instance where only two access units are daisy chained via their ICS tie-lines,
a resistor of not greater than 600 ohms must be maintained across the ICS tie-line in
order to avoid jeopardising station to station crosstalk results in RX mode at the high
frequency end.
When multiple transceivers are selected for simulcast operation, they are bound together at the
station output; thus, they are also bound together for other stations as well and defeat crosstalk
measurements. All measurements are based on single transceiver (TX) selection.
1.5.4 TRANSMISSION PRIORITY
Where Pilot and Co-pilot transmit simultaneously, the Pilot transmissions take precedence over
those of the Co-pilot. Co-pilot transmissions in this case would be rendered inactive.
1.5.5 INDUCED SIGNAL SUSCEPTIBILITY, RF SUSCEPTIBILITY, AND RF EMISSION
The wiring connections called out in Chapter 2 describe shield terminations for minimum ground
loop noise. The test harnesses used for RTCA/DO-160 Sections 19, 20, and 21 – Induced Signal
Susceptibility, RF Susceptibility, and Emission of RF Energy respectively – used shield
terminations at both ends of the cable. Should RF susceptibility pose a problem in a particular
installation, the installer may wish to try terminating shields at both ends of the cable. If this does
not produce satisfactory results, then double shielding may be required.
