In the beginning, calls were all received by the main City Hall switchboard operators. Those requiring police service were routed by a conveyor belt on top of the switchboard to a dispatcher (a policeman) in the remote-control room, who would broadcast it to the proper car . He then forwarded the information to the transmitting station in Elysian Park, where a second dispatcher would rebroadcast the call. This was to help insure that the message was received by the patrol officers. Elysian Park was the location of the 500-watt De Forest AM transmitter. Patrol Officers could receive calls, but could not "talk back" to the dispatcher.

Originally, 44 police cars were equipped with receivers. It was reported that "officers driving swift moving automobiles" took an average of only two minutes forty seconds to respond to any call in the city, so thirty-five additional car radios were added as soon as funds became available. The monthly report in June, 1931 indicated 12,644 radio messages were broadcast.
	KGPL on First Day of operation

Before long, it was recognized that the value of police radio could be better realized by a more streamlined method of call-taking. A new system was instituted, which increased speed in answering and dispatching calls. Now, police officers working the eight-position "complaint board" would receive all incoming public calls directly on a new "MICHIGAN 5211" telephone number, instead of having them relayed by the city hall switchboard. These officers were required to have at least five years experience in the field. Routine calls were then sent by the conveyor belt to the radio room, which had five dispatcher positions and a "link" operator.

When an emergency call such as a robbery or homicide was received at the complaint board, the officer could press a button and his telephone conversation would be carried over loudspeakers installed in the "Business Office Division," as well as in Robbery and Homicide Bureaus. This served both to alert detectives to a possible call for them, as well as to reduce the chance of human error by the board officer. Radio microphones were later installed at the complaint board, so the officer receiving the call could also broadcast it immediately

Soon, sergeants' vehicles also got radio receivers, and major calls could be answered by field supervisors as well as by the concerned patrol car. Divisional desk sergeants and detective offices were equipped with receiving sets. When the station supervisor felt it appropriate, he could send the division "emergency car" on a call. In the infrequent event - less than 1% of all calls - that the radio car officers did not receive the broadcasts, this ensured that the police were indeed responding, and provided the additional manpower that might be needed at a major incident.

LAPD broadcasts were monitored regularly by the Orange County Sheriff, the police departments of Beverly Hills, Alhambra, Santa Monica, Culver City, San Fernando, Hermosa Beach, Huntington Park, Burbank, Glendale, La Habra, Moorpark, and as far off as San Clemente, as well as the Orange County Fruit Patrol. LAPD had agreements with a number of police agencies to broadcast their emergency calls.

Between 1933 and 1936 the Los Angeles County Sheriff's Office and LAPD conducted a number of tests to determine whether police radio was adaptable to the mostly-rural Sheriff's patrols and constables. These were mainly done on busy weekend nights, and eventually the Sheriff decided that radio would work for his department. Until the county was able to get its own radio station on the air, LAPD began handling radio calls for eight of the sheriff's nine substations. Pasadena police were contracted to dispatch for the Altadena sheriff's station, as the Los Angeles transmitter didn't cover the foothill areas very reliably.

Los Angeles wasn't the first police department in the area to use radio, however. It now appears that the neighboring Pasadena Police Department had gotten on the airwaves almost a year earlier, sometime in 1930...

"Calling all cars, calling all cars..."

It should be remembered that the early 30's were the deepest of the depression years, and people didn't go out much.  And while radios had become very popular, good radio programs had not yet been developed.  Since police broadcasts were just above the AM broadcast band - LAPD was first on 1712 and then moved to 1730 kilocycles (kcs) - most home radios could tune them in. 

At night, the signal of LAPD could be heard all across the country, even as far as the east coast and Hawaii.

LAPD MAKES USE OF "PUBLIC" POLICE BROADCASTS

The PR and Community Relations aspects of the public "listening in" weren't lost on the Department either. On November 29, 1933, William Robson's radio series "Calling All Cars" debuted on the CBS Radio Network. Chief James E. Davis was right there from the get-go, being an announcer and narrator for most of the early programs, many of which were based on actual L.A.P.D. cases. This series was designed for two purposes..."to sell 'Rio Grande' Gasoline and to tout the use of radios in police cars.

As such, the stories revolved around just how fast squad cars can get to the scene of a crime now (1930s) as compared to a few years before, because of the radios ... and the increased speed and power of Rio Grande Gas! At times Davis sent subordinates to fill in for him, and many of the police officials that appeared as narrator, were just plain awful.  They were awkward, missed cues and lines and mispronounced just about everything."

In the early days of police use of radio, it was customary for a dispatcher to end a call broadcast by giving his last name. One of LAPD's first radio dispatchers in 1931 was Sgt. Jesse Rosenquist (1899 - 1966). Rosenquist, it seems, became quite famous across the country, because of the way he said his name. He had a deep voice, and he dragged out each syllable, "Rose-n-quist." So people everywhere became familiar with "Calling all cars, calling all cars...that's all. Rose-n-quist." In Southern California in the 1930s and early 40s, Jesse Rosenquist was practically a household word.

Listen to a few seconds of Jesse "Rose-n-quist"

So "KGPL" and "Rosenquist" and "Calling All Cars" and "That is all" began a tradition that later continued with Jack Webb's "Dragnet" and "Adam-12," in projecting the sounds and activities of the Los Angeles Police Department around the world.

As mentioned, originally 1712 kilocycles (kc) was the dispatchers' "talk out" frequency, but this was eventually changed to 1730 kcs to eliminate interference between Los Angeles and Pasadena police.

2 Way Radio

In 1936, the FCC issued an "Experimental Service" radio license to LAPD - W6XPA - for testing of 100-watt mobile transmitters in four police cars, to study the properties and usefulness of 2-way radio. These radios operated on 30.10, 33.10, 37.10 and 40.10 megacycles in what was then considered the ultra-high frequency band. It proved extremely successful, and in 1938 the Department began regular use of two-way radios. The cars still listened on 1712 kcs, but called in on frequencies in the 39 mc range. In 1948, these "talk-in" frequencies moved up to the 154-155 mc band (there were 7, plus the supersecret "frequency 9" for surveillance). Frequency 9 continues in use today as "Tac 1." 

As the city grew in the late 1940's, and radio traffic increased, a second dispatch frequency of 2366 kc was added for dispatching to the Valley, Harbor and West LA and Venice.