Elevator Intercom System Fiber Transmission Design Solution

The National Elevator Industry Standards Committee timely released the new standard GB7588-2003 "Safety Code for the Manufacture and Installation of Elevators" in 2004, and began nationwide implementation from 2005. The standard clearly specifies requirements for elevator communication systems in clauses 5.10, 8.17.4, 8.17.5, 14.2.3, and 15.12, covering not only multi-party communication for single elevator systems but also specific provisions for communication systems in multi-elevator cluster applications. The release of this new standard provides a scientific basis for the production, inspection, and acceptance of elevator installation projects in cluster applications.

With the widespread use of elevators, the elevator communication system has evolved from a simple single-elevator emergency call system into a multi-elevator group communication system capable of large-scale networking. This allows dozens or even hundreds of emergency call systems in large residential communities to be networked together, forming an elevator group communication system. In this system, each elevator has a fixed code, and the car main unit, car top sub-unit, pit sub-unit, and machine room sub-unit in each elevator can call and communicate with the management center in emergency situations. The management center can also call and communicate with any car main unit, car top sub-unit, pit sub-unit, or machine room sub-unit in any elevator, and can perform group calls and broadcast communication.

With long-term technical accumulation, elevator five-party intercom equipment has become increasingly mature, forming products with low cost and stable performance. The main technologies near the elevator are divided into two categories: common-line intercom (which does not distinguish terminal positions) and star-type intercom (which can distinguish car top, car bottom, car, and machine room). The former has simpler technology and lower equipment prices. The corresponding central equipment differs: the former uses multi-station direct-connect key terminals (such as the commonly used Otis five-party intercom), while the latter mostly uses bus-type dial terminals (such as Mitsubishi five-party intercom).

Traditional five-party intercom systems are implemented using twisted pair cables, which limits long-distance transmission. To address this, some manufacturers use ISM band radio, but since it is an unlicensed frequency band, rights are not protected and it is susceptible to interference. Others use GSM for remote transmission, solving the long-distance issue but requiring regular top-ups, which incurs significant ongoing costs.

The elevator five-party intercom solution using fiber optic or IP networks not only solves the long-distance transmission problem but also saves investment through a one-time cost. Additionally, through digital processing of voice, convenient voice recording is possible, easy integration with video surveillance systems, and access to multimedia command and dispatch systems, enabling interoperability with wireless cluster intercoms, fixed telephones, and mobile phones.

The five-party intercom fiber transmission equipment (referred to as five-party intercom optical terminal) provides access channels for existing elevator intercom equipment. While keeping the existing remote equipment unchanged, it provides an audio channel for each elevator (identifying which terminal is currently speaking through signaling encoding).

When providing optical transmission channels, the equipment at both ends remains unchanged. This only solves the transmission problem without enhancing other functions, resulting in higher system costs.

Therefore, we provide a terminal comprehensive solution. On the central equipment (DTZX), we offer two telephone interfaces, a computer communication interface, an emergency response button, indicator lights, and an alarm speaker. It can be networked with other devices, expand more optical ports, and provide an Ethernet interface for IP recording. It can connect up to 120 elevators.

The emergency response button is used when no computer is involved (e.g., shutdown, crash, power failure). Pressing this button automatically connects to the currently alarming elevator. After handling, if the alarm light remains on, pressing again connects to the second alarming elevator.

Another advantage of using fiber optics is that each elevator has an independent channel, avoiding contention for the voice bus, facilitating centralized recording.

The fiber transmission system has automatic line detection capability for each node device, with automatic fault alarm.

Central equipment functions: When any remote intercom device goes off-hook or alarms, the alarm light on the central equipment panel lights up, sending the channel number and alarm content to the PC. The corresponding button on the screen turns red. When bound with images, the elevator's image information is displayed. Pressing the corresponding button on the touchscreen connects the first telephone to the elevator for five-party communication. If the first telephone is busy (already connected to an incoming call), it automatically connects to the second telephone (if already off-hook, direct communication; if not, ringing).

The central unit can directly call the remote end: first go off-hook, then press the corresponding elevator button to achieve five-party communication.

In emergency situations, pressing the emergency button allows the central unit to broadcast to all elevators.

The PC can generate statistical reports.

There is an elevator data input box (allowing input of all elevator data for each building, as well as maintenance personnel mobile numbers and cluster frequencies). When an alarm occurs, the specific location of the elevator is displayed (such as building number, elevator number, number of elevators, number of floors, etc.).