Instruction manual

ACU-1000 Operations Manual
2-98 Interoperability Now
• F1 Function Tone, 1950 Hz for 40 msec @ 0dB.
• Hold Tone, 2175 Hz @ -20dB, mixed with the TX program audio as long as PTT is enabled
(also called the “Low Guard Tone”).
The levels of the EIA keying tones are expressed relative to the normal TX program audio.
When the DSP-2 is set for default TX audio (0 dBm) into a terminated 600 Ohm load, the
levels are +10 dBm for the High Guard Tone, 0 dBm for the Function Tone, and –20 dBm for
the Low Guard Tone. Since the maximum output of the DSP-2 is +10 dBm, and the High
Guard Tone level is 10 dB above the program audio, the program audio must not be set higher
than 0 dBm if EIA Tone Keying is used. The Keying Tone Amplitude configuration item does
not affect the EIA keying sequence tone amplitudes.
2.17.2.11 COR Inhibit Time after PTT
Some types of radios produce momentary, unwanted COR outputs just after their PTT inputs
are de-activated. If a radio connected to the ACU-1000 exhibits this behavior, the COR inhibit
causes this COR to be ignored. If the COR inhibit time is not correctly set, this COR signal can
cause connected extensions to momentarily key.
The factory default is 100 ms.
2.17.2.12 PTT or COR Priority (Half Duplex Only)
For most applications, the standard setting is PTT priority, the factory default. PTT Priority
indicates if a system operation calls for the radio to begin transmitting, it will always do so,
unless a previous PTT is in active use for this net. For example, if two DSP modules (modules
1 and 2) are connected in a net, with neither module receiving a signal and module 1 begins
receiving a COR (valid signal), module 2 will key. If at this point, module 2 begins to receive a
COR, it will not switch to receive because the module is set to PTT Priority. Only when the
existing COR and PTT scenario goes away, will module two generate a COR, and then key
module one.
PTT or COR priority only matter if the radio or other equipment connected to the DSP-2 or
RDI-1 is half duplex (can not transmit and receive simultaneously). If a full duplex radio is
used, PTT and COR can occur simultaneously, so there is no reason to set to COR priority, and
the module should be left in the PTT priority default.
In some requirements, it is necessary for COR to have priority over PTT. This indicates as
long as a radio is receiving a valid signal (as indicated by the detection of COR), the DSP-2 or
RDI-1 module will not put the radio into the transmit mode. One example is when a PSTN-2
module and DSP-2 module cross-connect a phone line and radio together. If the PSTN line has
high background noise, COR Priority will probably be useful.
PTT priority is the factory default setting.