The full form of EOW is Engineering Order-Wire.

Purpose of this paper is to describe the hardware design implementation of the Enigneering Order Wire. Engineering Order
Wires (EOW) allow field engineers to communicate during installation, commissioning and maintenance of
telecommunication networks. EOW must be robust and shall operate with a minimum of resources even if parts of the
network are out of service.The EOW-system is capable of functioning in a ring.These functions have made the EOW-system
in large number of PDH-installations and simple SDH networks.

The DTMF-EOW (Dual Tone Multi Frequency – Engineering Order Wire) is a System which provides network wide Telephone service functionality between Telecommunication sites over a single (embedded) 64kbps channel. Since In-band/channel DTMF tones are used for signaling, this module is called as DTMF-EOW. This is to Minimize the Bandwidth required. When the module is used in an SDH network the 64 kbps channel is normally placed in SDH section overhead byte E1 or E2.

Since the E1 and E2 bytes are multiplexed in to the SDH frame at the final stages of transmission the impact of network infrastructure on these bytes is very less. Hence as soon as the Communication medium (optic fiber) is
good communication is guaranteed for the users. This feature will help the customers to install/ configure/ maintain their Equipment properly. Apart from this, special features are also included for enhancing the performance of the system. These Special features includes selective calling, group calling etc. The digital EOW format is DSC proprietary. The bit rate is nominally 126031 bit/s. Of this only half or 63kbit/s is the actual voice data. The digital EOW signal is sent between modules via cables. The physical format here is ITU V.11.