Popcom (an abbreviation of Popular Communications) was a line of modems marketed by the Prentice Corporation of Sunnyvale, California, introduced in 1984. The line comprised six models—X100, X150, C100, C150, C200, C250—the C models being internal modems meant to plug into a free ISA expansion slot of an IBM PC compatible, while the X models were compact external units intended to be plugged into a wall indefinitely and connected to the computer via a serial cable. The X100 and X150 were noted by the press for their very small physical footprint among its contemporaries in the market. The whole line-up of modems were largely compatible with the Hayes command set for modem–computer communication, although Prentice programmed an extended feature set onto their ROMs, which allowed the modems to recover from temporary hiccups in transmissions and switch between voice communication and data transmission nearly on-the-fly. Although a successful product for Prentice, making the company one of the top manufacturers of modems for IBM PC compatibles, it could not save the company from filing for bankruptcy in 1989, after which the Popcom modem line was discontinued.
Overview
X100 and X150
The X100—the flagship product in the Popcom range—is an external modem, housed in a beige plastic case with a built-in AC power adapter. Its two-pronged (non-polarized) plug is molded into a swiveled hinge, allowing it to hug the wall when the modem is plugged directly into a wall socket (the prongs perpendicular to the socket and the rest of the unit parallel) or be plugged into a power strip (the entire unit perpendicular to the strip). The three communications ports of the X100 include the RS-232 serial port (a female DB-25 connector), a modular 6P6C port for telephone handsets, and a modular 8P8C port that connects the X100 to the wall phone jack. The communications ports are located opposite the AC plug, or at the base of the modem when the modem is plugged into the wall. The X100 measures 7.8 by 4.7 by 1.6 inches (19.8 by 11.9 by 4.1 cm)—not including the plug, which contributes to 0.7 in to either the length or depth, depending on the direction it faces. The plug cannot fold down into the unit. A dimple in what is normally the rear of the unit contains a radial potentiometer in its center, which adjusts the volume of the modem's internal speaker. When the X100 is plugged into a wall socket, the speaker faces flush to the wall, so ventilation slots are included to let sound out through the sides of the unit. The X100 otherwise contains no switches or status lights, not even for power. The only status indicators on the unit itself are provided through aural means, via short bursts of three touch tones generated from the speaker. Each burst indicates whether the user has correctly performed a step in the initialization process for the X100. The recommended order of operations to initialize the X100 is to first plug the modem into mains power, then to connect the X100 to the computer or terminal, and lastly to connect the X100 to the wall phone jack. If the user performs these steps out of order, several bursts of tones will sound together when the final connection has been made. Prentice intended for users to have the Popcom plugged into a live socket at all times; the X100 consumes about 4 watts of power on average, or the same as an average 1980s-era nightlight. Its minimalist design was intentionally inconspicuous, and being plugged into the wall meant saving desk space. The X100 has a maximum transmission rate of 1,200 bit/s, switchable down to a maximum of 300 bit/s. It is compatible with both the Hayes command set and the Bell 212A modulation scheme. Prentice laid out three Hayes commands that could not be utilized by the X100, namely echoing and those pertaining to transmitting over amateur radio, but these were seldom used by the vast majority of personal computer users. The X100 can transmit in one of two modes: in strict Hayes compatibility mode, in which the X100 only issues commands with the Hayes set, and in Popcom mode, which grants the X100 more advanced features. In Popcom mode, the modem can detect if it hears a human voice on the line, if it hears a Bell busy signal, and whether the system on the other end of the line is transmitting too fast or too slow for the Popcom to handle. Popcom mode also offers 19 additional command sets for tuning the number of seconds it will take for a data connection to be established before it times out; for tuning the number of seconds the transmission can tolerate in disruptions; for changing the escape sequence used by the Popcom to switch between transmitting and receiving; and so on. Setting the tolerance for disruption length was useful, for example, for subscribers of telephone services who had call waiting service, a byproduct of which is the zip tone used to indicate an incoming call from another person during a preexisting call. Such a zip tone occurring during a data transmission usually proved fatal for the connection, but the Popcom could have carried on after such an interruption and continue receiving data, albeit with errors in the stream, which may have been correctable with error detection schemes and retransmission capabilities of some online services contemporary to the Popcom. The human-voice detection capability allowed users to transmit data and speak to the recipient on the other end of the line within the same call. This was useful in the case of remote jobs that required debriefing before the transmission of data—sometimes multiple times in the same job. Performing both these duties, and being able to switch between the two, during the same call meant saving time and money, as placing multiple landline calls during the 1980s was sometimes a costly affair—especially for long-distance connections. This feature, however, was contingent on both the caller and the recipient having Popcom modems. The X100's successor, the X150, was virtually identical to the X100. The X150 however came bundled with pfs:Access for MS-DOS, a terminal emulator by Software Publishing Corporation.
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