Tyco Electronics MM23772 8.19 DIGITAL VOICE OPERATION

8.19 DIGITAL VOICE OPERATION

Digital voice programmed systems have three (3) different voice modes: clear (analog), digital, and

private (encrypted). The voice modes are programmed on a per-group basis within each trunked system.

The Clear Mode is a voice mode in which the radio transmits and receives only clear (analog) voice

signals. These analog signals are non-digitized and non-encrypted. Clear mode transmissions can be

monitored easily by unauthorized persons.

Groups or channels programmed for clear operation cannot transmit or receive digital or

private messages.

The Digital Mode allows the radio to transmit and receive digitized voice signals. Digital signals provide

improved weak signal performance and cannot be easily monitored with a standard receiver. Groups and

channels programmed for digital operation transmit only digital signals. Message trunked group calls and

individual phone calls (I-Calls) are answered back in the mode in which they were received assuming the

call or hang time is still active. Individual phone, all call, and emergency calls are transmitted clear if the

digital mode is disabled or inoperative.

If receiving an analog message trunked call, the radio responds in the analog mode during the hang time

on the working channel.

If receiving an analog I-Call, the radio responds in the analog mode during the hang time.

When using the *WHC* feature to respond to an I-Call (after the hang time has expired), the call is

transmitted in the mode defined by the system mode as programmed for the current system if the ID being

called is not in the I-Call list. If the ID is in the I-Call list, then the call is transmitted as defined by the I-

Call mode programmed in the list for that ID.

The overdial DTMF tones are not available while in the Digital Mode.

The Private Mode allows the radio to transmit encrypted messages and receive clear or private

transmissions. The radio transmits private if the group/channel is programmed for private operation and

forced operation is pre-programmed. If autoselect operation is pre-programmed and the radio is in the

Private Mode, the radio transmits in the mode of the received call if the hang time is active. If no hang

time is active, the radio transmits private.

Cryptographic keys are transferred to the radio using a cryptographic Keyloader. Up to seven (7) different

cryptographic keys, numbered 1-7, can be transferred from a Keyloader and stored in the radio. An

individual key is automatically selected on a per-group/channel basis according to the radio programming.

Groups and channels within the digital system can be programmed for keys 1-7 (private). Up to 8 banks

of 7 keys can be stored for private systems. The bank is specified per system.

When operating on a group or channel programmed for Private Mode, all transmissions are private

transmissions and the radio receives clear and private signals. The status icon is displayed when the

Private Mode is enabled. If the selected group or channel is programmed for auto-select capability, the

mode may be toggled between private and clear with the  key, then following the selection mode rules.

Radios programmed for forced private operation do not allow a change of the transmit mode.