About 35 years ago, access control systems emerged on the market as customized microprocessor-based host processors connecting to field panels (multiplexors or data gathering panels) and, from there, to field devices such as card readers and electric locking devices. More advanced security systems might include change-of-state (binary) devices such as door position switches, request-to-exit devices and other point and volumetric intrusion detection equipment. Anything more sophisticated, such as analog inputs, required custom systems and software - typically mounted on DEC PDP platforms.
Things have definitely changed dramatically for security end-users since then. With the advances in IP-based technologies, end-users are now able to integrate many different technologies and devices into a common access control system.
In the past, field devices were hardwired to access control panels and the panels communicated to the host processor via serial data transmission on dedicated copper or via modems on POTS (Plain Old Telephone Service) lines at 100 baud or 100 bits per second (300 baud if you had a fast system). To put these data rates in perspective - at 100 baud, it would take about one second to send the word "transmission." This compares to today's data rates measured in Gigabits per second - a 1 gigabit/sec rate would send this complete article 10,000 times in one second.
The low transmission rates back in those bad old days meant that data packets had to be kept short. An alarm signal would consist of a channel number and a panel number while an access control transaction sent the card number with reader/channel and panel number. The time and date stamp might be generated by the panel or at the host. A two- to three-second delay between a card read and a door unlocking was considered acceptable.
While audio transmits well on POTS lines, video was virtually impossible over voice-grade lines until the advent of Slow-Scan about 20 years ago when single-frame, low-resolution, black-and-white shots could be sent every few seconds - usually on dedicated lines. This ushered in volumetric intrusion detectors with built-in cameras that could transmit a series of still shots over the alarm lines to help reduce false alarms by identifying the cause of an alarm. However, the quality of the video was far from optimum and carefully designed scene lighting was needed to provide any chance of recognizing any perpetrators.
Although line-of-sight, long-distance video signals from analog cameras can also use infrared or microwave transmission, home run coaxial cable was the norm - achieving distances close to 1,000 feet using heavier cable (RG-11U). Unshielded twisted pair (UTP) cable, using active baluns, is another solution; UTP can achieve video transmission from analog cameras up to 1.5 miles.
The bandwidth (transmission rates) available on today's local and wide area networks (LANS & WANS) have opened up the flood gates for security applications. It started slowly with IP-addressable access control panels connected via network switches to the corporate LAN to eliminate the duplication of "trunk" cabling to the security system "host" (server). And connection of the security system server to the WAN provided inexpensive global connections via the Internet and Virtual Private Networks (VPN).
Next followed the introduction of digital video recorders (DVRs) to replace those dysfunctional (by today's standards) VCRs and provide integrated video switching and display. Video signals were still analog and required conversion to digital through an encoder, but with the addition of a network card, the DVR became IP-addressable and its digital content could be made available on the network for other administrative workstations (PCs). The network connectivity of the DVR also made for better interactive communication with the access control system.
Pushing Access Control to the Edge