Motorola BMD
The Motorola BMD is a radio transmitter . It is used to alert or notify people or groups of people via a radio network. The device is mainly used by the BOS . The device is portable and can also be worn on a belt thanks to its clip on the back.
technical description
The standard version of the Motorola BMD works in the 4-meter band , while there is also a version for the 2-meter band . The receivers must be doctored and adjusted for the respective radio channel . The alarm occurs in the same way via a 5-tone sequence , to which the device must be specifically coded. The coding of the tone sequence (s) takes place via an integrated circuit (IC) . The device can be coded on up to two such 5-tone sequences, which may only differ from one another in one digit within the last three digits (group call function). Examples:
- Possible coding: 12345 + 12347 or 12345 + 12335 or 12345 + 12445
- Impossible coding: 12345 + 12352
If one of the coded five-tone sequences is received, an alarm tone sounds first. This can be an intermittent beep or a continuous tone, depending on the five-tone sequence recognized. Then the receiver is opened and the radio communication is audible. If no signal or carrier is received for a certain period of time, the BMD goes into "Call reminder" mode. The receiver is muted again and a short beep sounds every 30 seconds. A rotary switch on the front of the device is used to switch on the device and to adjust the volume. The volume can be set in two different volume levels. There is also a button for resetting the FME after the alarm announcement has ended (the FME is muted again and is ready to call). A 2.5 mm jack socket is used to connect an earphone.
With a second, optional rotary switch, the device can be used to monitor radio traffic. As a further option, the second rotary switch enables the so-called "Mem-O-Lert" function to be used. If the switch is moved to the "M" position, an incoming alarm is not immediately output, but only when the switch is reset from the "M" position.
The detector is powered by a special 2.6 volt rechargeable battery that was manufactured by Motorola. These batteries are now also available from other manufacturers.
The beep sound is composed of two frequencies. A "beep frequency" is 2750 Hz and an "on / off frequency" is 4 kHz.
Areas of application
The device was introduced in 1984 and was the successor to the Motorola Pageboy II . The BMD is still widely used today by many organizations that issue analog alarms. In addition to being used on a full-time basis by the rescue service or fire brigade , the device is widespread , especially in disaster control and aid organizations, due to its simple handling, its limited range of functions and its low cost . In addition, the device is often used under adverse conditions (construction site, factory floor, etc.). On the one hand, this is due to the very high volume of the device and its robustness against external influences (solid housing, loudspeaker protected against dust).
Of radio amateurs especially the 2-meter band devices are often converted 2-meter amateur radio band for that and for alerting the emergency radio used.
equipment
The following accessories were manufactured for the BMD:
- 230 volt charger with charging point for an additional battery and external connection options for an antenna and additional devices such as B. an alarm whistle.
- Home / vehicle add-on with an additional 2-watt audio amplifier with external connection options for an antenna, an additional loudspeaker and additional devices such as B. an alarm whistle.
- Various leather bags, some with a towing antenna (in poorly served reception areas)
Footnotes
- ↑ http://www.bmd-kodierverbind.de
- ↑ Motorola, operating instructions for the BMD signaling and alarm receiver