ZETRON 2000 Series Specifications download pdf (Page 158)

Theory of Operation

158 025-9035AA

MF Decoder Option

When activated by the Dual trunk software, and enabled in the configuration settings, the

78A207 MF decoder chips on the MF board will generate an interrupt to the Dual Trunk's

CPU when an MF tone pair is decoded. The CPU reads the MF board's status to determine

which half of the dual trunk generated the interrupt, and which MF tone pair was received.

The MF board can also generate MF tones, using an 87C751 and a DAC. The MF tone

frequencies are listed in Table 18. For comparison, the standard DTMF tone frequencies

are listed in Table 19.

Station Card

The Station Card provides interface to the transmitter or transmitter controller. The Station

Card is responsible for making the paging tones, directing the voice to and from the PCM

highway and providing the necessary inputs and outputs to control the transmitter(s).

Station Card II (702-9441)

This version of the station card takes advantage of advances in IC design and components

in general since the original station card was designed.

The CODEC in U19 handles sending voice audio both to/from the PCM data bus and to

the transmitter. The amplitude of transmitted voice audio is set with R9.

The paging tones are produced by U7 and RP3. The amplitude of the transmitted tones is

set with R8.

This card provides a high-stability oscillator for digital paging. As a result, it also provides

better “batching” performance than the previous model of station card.

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ZETRON 2000 Series Specifications Page 158