Instruction manual

ACU-1000 Operations Manual
1-8 Interoperability Now
Figure 1-4 Telephone Cross-Connection
Within the ACU-1000, the PSTN module performs the 2-wire to 4-wire conversion. For a two-
way conversation between a telephone caller and a radio user, the telephone system would be
interfaced to a PSTN module. Within the ACU-1000, that PSTN module would be cross-
connected to a DSP module, which provides the radio interface.
In Figure 1-4 above, the external interface of the ACU-1000’s PSTN module is simple a pair of
wires carrying 2-wire audio. The PSTN module VOX function detects any audio being spoken
over the phone and causes a PTT signal to be sent out by any cross-connected DSP modules,
along with the phone input audio. If the portable radio A is transmitting, the associated radio
interfaced to the DSP module receives this audio and sends it to all cross-connected modules.
The PSTN module places this audio on the 2-wire pair and sends if off to the telephone system.
In the ACU-1000, the incoming VOX or COR inputs are reported to the CPM module. The
CPM module then commands any cross-connected modules to activate their PTT outputs.
Incoming audio is placed on a rear panel audio bus, where it is picked off by any cross-
connected modules for retransmission.