Antenna of Radio Equipment Raised by Compressed Air-Car Carries Portable Transmitter and Receiving Set

RAPID communication is one of the most vital and necessary adjuncts to our modern civilization. Help could be within a few miles from victims of tragedy, and without communication, their plight would not be known.

Let us assume for instance a disaster has occurred, where a number of people are killed and/or are injured, or where property and life are threatened, whether it be an explosion, earthquake, fire, train wreck or flood.

Help is needed. Emergency services arrive at the scene. Time is an important factor. Outside help and equipment are needed, help already on the scene has to be directed, and co-ordinated so as to be effective. Communication is vital.

Speaking Into the Microphone of the Disaster Unit

The communication equipment has been designed and constructed by the Alarm Division of the Portland Fire Department. It has been built for the utmost flexibility, practicability, and ruggedness possible within the space available.

It consists of several units. The main power amplifier has an audio output in excess of two hundred watts, with very little distortion.

This basic unit is housed in a rugged steel rack mounted and cushioned with heavy rubber. It may be used to amplify the output of the radio receiver, microphones, or telephone. The output is primarily used to supply energy to the loudspeaker and the radio transmitter.

The loudspeaker, developed by the Fire Bureau, is an original design, consisting of a quadruple driving unit, with a continuous, undistorted output of 120 watts of audio power, feeding a very compact directional horn. This horn, being equal to four of the conventional heavy duty six foot trumpets, is mounted complete in a 50-inch circle, by 14 inches depth. When driving, the entire speaker assembly is dropped down flush with the top of the car. When raised, it can be turned in any direction and tilted to any elevation. In this way, the sound may he directed to any desired point, such as the top floors of a building, or to a ship on the water. While complete tests have not been made with this speaker, it is known that intelligible speech may be transmitted approximately two miles in the open.

Sending Set

The radio transmitter operates on an ultra high frequency, with an input power rating of 100 watts. It may be fed from any of the microphones, telephone line or radio receiver. It will normally be used for communication with the police radio system and the small portable transmitter carried by this car. In emergencies, communication with other services such as government agencies and radio amateurs, can be carried on. While the range is a variable factor, dependent on many conditions, it will give satisfactory results over a distance of 50 miles, under any ordinary conditions.

The antenna is raised by compressed air, when it is desired to use the radio equipment, and is then dropped down out of the way when the car is “running.”

The radio receiver is a high grade communications type, which will tune to all frequencies between 520 and 40,000 kilocycles (575 to 7.5 meters), which range includes the broadcast band and all police frequencies.

Portable Receiver

The portable receiver and transmitter is a waterproof “Pack Set” weighing 17.5 pounds complete, ready for operation with a water-proofed telephone handset, or a special gas mask, with a built in telephone receiver and transmitter may be used. No tuning is necessary on this unit, the operator merely pushes one button to receive and another to transmit.

Both the transmitter and receiver are tuned to the same frequency as the car. The transmitter is crystal controlled, the same as large units. The tuning controls are locked and entirely covered up with a protecting plate over the top of the case.

While this unit is primarily intended for working from inside of burning buildings, etc., to the outside, or over the loudspeaker, it has been heard for a distance of 15 miles.

In addition to the main radio receiver, a special “police receiver” is installed operating from the car battery, on an independent antenna. This unit is tuned to the Oregon Municipal Police Frequency and may be operated independently. at any time.


Microphone equipment consists of one microphone, mounted on a flexible arm inside of the car. one microphone mounted on a combination stand, one hand microphone, one telephone handset, and 400 feet of flexible microphone cable in various lengths. The external microphones are plugged-in on either side of the car. Direct communication may be carried on through the radio with the fire alarm office by plugging the cable into any fire alarm box, or any phone line may be plugged into either side of the car.

A carefully chosen kit of accessories, such as headphones, spare microphone, telegraph key, and spare tubes complete the equipment.

The amplifying and radio equipment operate from any standard 110-volt A. C. power line, or from either of two gasoline driven generators located within the car.

This unit was christened at the I.A.F.C. convention at San Francisco.

Industrial Fire Problems

The Industrial Fire Prevention Association of Wilmington, Del., meets the first Thursday of each month in Fire Station No. 1, Wilmington, to discuss industrial fire problems.

The membership of sixty persons consists of watchmen, janitors, chiefs of the various industrial plants, and safety men.

During Fire Prevention Week, a public meeting is held at the Wilmington Public Library, and a guest speaker is obtained. At the last such meeting T. Alfred Fleming spoke, and the attendance was 250.

New 100-Foot Power Operated Aerial Truck for Washington Above is shown the new 100-foot power operated aerial ladder truck recently delivered to Washington, D. C., by Peter Pirsch & Sons Co., of Kenosha, Wis. The job is equipped with an aluminum alloy aerial ladder, hydro-mechanically operated.
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