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QSK operation is a technical challenge: It requires very fast T/R RF switches at the high power and voltage side of the radio transceiver. Such switches must be controlled automatically by the telegraph key, and as such they must be rapid enough to be perceptually undetectable by the telegraph operator.
A general option setting for all MDC systems is to enable or disable an acknowledgement (ack) data packet. For example, following a selective call, the called radio replies with an ack. This data "handshake" confirms the called radio is powered on, has received and decoded the call. The encoder beeps to confirm the call got through to the target.
A shackle code is a cryptographic system used in radio communications on the battle field by the US military, the Rhodesian Army, and the Canadian Army, among other English speaking militaries which might not distribute or require sophisticated one-time use pads. It is specialized for the transmission of numerals.
Joint Tactical Information Distribution System Users, 1990. The Joint Tactical Information Distribution System (JTIDS) is an L band Distributed Time Division Multiple Access (DTDMA) network radio system used by the United States Department of Defense and their allies to support data communications needs, principally in the air and missile defense community.
A Radio code is any code that is commonly used over a telecommunication system such as Morse code, brevity codes and procedure words.
Newer NSA systems allow "over the air rekeying" (OTAR), but a master key often must still be loaded using a fill device. NSA uses two serial protocols for key fill, DS-101 and DS-102 . Both employ the same U-229 6-pin connector type used for U.S. military audio handsets , with the DS-101 being the newer of the two serial fill protocols.
Some systems still use Modat today. Modat is used for unit ID and emergency buttons, rather than for selective calling. In a typical installation, each radio in a system is assigned a unique seven-tone code. Each time the radio's push-to-talk button is pressed, the radio transmits the seven tone sequence at the beginning of the transmission.
In digital modulation, minimum-shift keying (MSK) is a type of continuous-phase frequency-shift keying that was developed in the late 1950s by Collins Radio employees Melvin L. Doelz and Earl T. Heald. [1] Similar to OQPSK, MSK is encoded with bits alternating between quadrature components, with the Q component delayed by half the symbol period.