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RF Technology T800 Page 9
2 TRANSMITTER INTERNAL JUMPER OPTIONS 2.10 JP17: Bypass Low Pass Filter
a link across it will bypass the low pass filter.
In conjunction with this change, it sometimes may be necessary, depending on the type of
trunking controller used, to add a 100K resistor in the place reserved for R157.
2.11 JP19: Alarm Output (Rev 4 or higher)
The main audio transformer (T1), is connected to the Line IP1 and Line IP4 pins on P3.
These two pins constitute the main audio input for the exciter. The centre taps of the audio
transformer, though, are brought out on Line IP2, and Line IP3. These can be used as
alternate audio pins for larger signals, or to directly access the dc loop sense circuitry. JP19
allows an alternate use for Line IP2 (pin 7 of P3). In the alternate position for JP19, the
ALARM signal (the signal that drives the ALARM LED itself) is connected to pin 7 of P3.
The ALARM signal when asserted is low active; when unasserted, it pulls high to +9.4V
through an LED and a 680 ohm resistor.
Condition Position
P3, pin 7 connects to center tap of transformer T1 1-2*
P3, pin 7 connects to ALARM signal 2-3
2.12 JP22: Use Tone- as a Direct Digital Input (Rev 4 or higher)
JP22 is normally shunted with a jumper, which connects Tone- on P3 (pin 18), as the negative leg of the
Tone input pair. Removing this jumper disconnects Tone- from this path and allows the use of the
should be in the alternative position (Direct Tone Input).
2.13 JP23: Connection of DMTX Board (Rev 4 or higher)
When a DMTX board is connected to an exciter, there is provision for digital or audio modulation of the
reference osciallator and the VCO. The digital signal is input via the DB9 rear connector and the audio
input signal is via the Line inputs on the standard DB25 rear panel connector.
