Friday, June 8, 2018

The Origins of Radio Paging

Radio paging systems existed for about 50 years and was a leading wireless technology until the cellular industry exploded. 

Volunteer fire departments, doctors, service companies, construction workers, salesman, businesses and private citizens once used this technology extensively.  Today, principally volunteer fire departments and the medical profession continues to use radio paging.

Pagers, or more commonly known as  “beepers” , are not extinct but have seen a massive decline in users resulting in declined revenues. At the height of the industry [1996], revenues exceeded $4.4-billion.  By 2011, the industry was down 90% [$489-million].

The evolution of paging receiver variations included tone only, tone & voice, numeric and alphanumeric digital signaling, as well as talk-back paging.  You wanted to page someone, you would dial a phone number, leave a voice message, a call back number, or enter a digital message.

However, before all this automation and the ubiquitous "beep – beep - beep" heard from activated pagers, technology was quite deferent and evolved quite rapidly as an essential service.

Prior to the paging industry, those requiring 24-hour answering services generally subscribed to a telephone answering service company.  If you could not answer your calls or were away from your telephone [or didn't have a secretary to answer calls], you would let the telephone answering service know of your unavailability [by phone]. The answering service would then answer calls and take messages.  At a later convenient time, you would call the answering service to obtain your messages from the missed calls. Later, answering services used paging to notify the subscriber of messages.
Florac Paging Receiver

In the early 1950s, Telanserphone, Inc., an early telephone answering service located in New York City, whose owner, Sherman Amsden, was looking for a way to contact customers that they had a message.  Richard Florac, another New Yorker, was approached by Amsden to develop a receiver to alert customers of messages.  Florac designed the pocket receiver and obtained a patent in 1952.  Amsden under Telanserpone and also Aircall were the first companies to utilize this new technology – radio paging.

The first paging receiver was comprised of an aluminum case that included a battery, two miniature vacuum tubes, an activating switch, a tuner, a speaker, two dry cell batteries, and a drooping wire antenna.  The radio electronics used was an amplitude modulated [AM] superegenrative receiver/detector operating on 43 MHz.

Both vacuum tubes were pentodes.  A CK522AX tube, connected as a triode, was used for the RF section and a CK533AX was used an audio amplifier.  One battery provided voltages for tube filaments and the other battery was used to supply plate operating voltages.

The paging broadcast system was comprised of a high power AM transmitter [typically 250 Watts] operating on 43 MHz.  The transmitter was interfaced with a magnetic tape recorder that was set up in an endless loop.  Subscribers to paging services were typically assigned a three-digit number.  A telephone answering service operator would receive a message, then record the subscriber’s three-digit code on the recording tape.

The tape would be updated every fifteen minutes or so and would list the three digit code of subscribers who had messages.  The transmitter would continuously broadcast the revolving tape with user codes and removed after the subscriber called in for their message.

Subscribers would obtain their messages by holding their receiver’s speaker to their ear; they would depress the switch to activate the speaker, if the message was not clear they could “tune” in reception by moving the tunable knob on the receiver.  They would then listen to the tape and listen for their number.  If their number came up on the tape, they would find the nearest telephone and call the answering service for their message.

Later systems evolved to selective calling a pager, alerting individual pagers. The telephone operator would enter the three digit [or other] code on a manual encoder that would generate and send unique signaling tones [dual tone, two-tone sequential] to the transmitter for broadcast. The paging receiver set up on this tone sequence would then beep when activated.

Systems continued to evolve and were interconnected to telephone systems where paging terminals would perform call answering,  generation and delivery of signaling codes, and then messages to subscriber units.
Of course they were not called pagers in the beginning but pocket receivers.  Motorola coined the term Pager in the mid 1950s when they introduced the Handie-Talkie Radio Pocket Pager -  it was the first individual [selective calling] pager. It was also the first receiver utilizing transistors and   Thus the first true “beeper” frequency modulation [FM].

Motorola was a giant force in this industry as they had 80% of the hardware market.  With the decline if paging services, Motorola officially left the paging market in 2001.

Florac AM pagers were still used until the early 1970s until the FCC required that paging systems convert to FM modulation. 

In the late 1960s and early 1970s, Airsignal International, Inc.[AI], which became the largest Radio Common Carrier of that era, were the first to introduce NEC pagers labeled as their brand for their nationwide paging services. AI was one of the first nationwide telephone answering and paging service companies in the US, having operations in many US major cities as well as internationally.