MDC-1200

They are typically incorporated in high-end analog FM commercial and public safety radios made by Motorola and other manufacturers.

A general option setting for all MDC systems is to enable or disable an acknowledgement (ack) data packet.

The ack packet takes roughly the same amount of air time as the selective call itself.

In the leading option, the data burst is sent at the moment a user presses the radio's push-to-talk button.

An option can be set to make the radio's speaker emit a tone for the length of the unit ID data, (about 1-1.5 seconds).

The leading unit ID takes slightly more air time (is longer) than a trailing ID because of a header tone and the need to delay the data burst to allow time for CTCSS decoders and voting comparators to open an audio path to the decoder.

This avoids timing issues because the audio path to the base station is already open.

The standard Motorola encoder-decoder has a display which shows the most recent four-digit, push-to-talk ID.

It would print the unit ID and the time it was received based on the decoder's internal clock.

The radio will silently send the emergency message, with the four-digit unit ID embedded, three times.

In a computer-aided dispatch (CAD) environment, the button press may pop a dialog box or activate some other attention-getting device.

Some MDC-equipped radios have buttons which allow pre-defined status messages to be sent to the base station decoder.

By pressing a series of keys on the encoder-decoder, the base station operator can send a data packet that activates a lighted indicator or makes the radio beep.

This tended to produce a lock-in situation where many companies and public safety agencies were restricted to using mostly Motorola radios, in order to ensure compatibility with existing systems.

Manufacturers of third-party MDC-1200 hardware, including in-radio encoder/decoder modules (as aftermarket add-ons for non-Motorola radios), display units for dispatch centers, etc.

Some of these products have display screens, some are 'black boxes' with inputs for power and receiver audio, and an RS232 serial data output.

While the USPTO still shows them as active patents, a number of other radio manufacturers have begun including MDC-1200 support in their products.