Monolog Exchange Interface Kit

Monolog Exchange Interface Kit (MEIK)

In exchanges where multiple Monolog units were installed, the early arrangement was simply to stand them on a shelf with a number of MIUs mounted above — functional, but informal. In later years, a purpose-built solution was introduced: the Monolog Exchange Interface Kit, universally known as the MEIK.

The MEIK is a small, lockable, wall-mounted metal enclosure capable of housing up to four Monolog units. Rather than individual MIUs, the interface electronics are consolidated onto a single backplane PCB inside the enclosure, with each circuit section handling one Monolog. This made exchange installations considerably neater, more secure and easier to manage.

Early Exchange Installations

Before the MEIK was introduced, Monologs were deployed on open shelving within the exchange, with individual MIU units wired above each logger. The photograph below — from an exchange installation of the era — shows this arrangement, with a shelf of blue Mark I Monologs connected to their respective MIUs.

Multiple Mark I Monologs installed on a shelf in a telephone exchange — Early exchange deployment — Mark I Monologs on a shelf with MIUs mounted above. The shelf label reads 'MONOLOG'. Click to enlarge.

The MEIK Cabinet

The MEIK enclosure is a grey, lockable metal cabinet, rack-compatible and wall-mountable. The photograph below shows a MEIK installed in an exchange equipment rack, circled in red.

MEIK cabinet installed in an exchange equipment rack, circled in red — MEIK cabinet (circled) installed in an exchange equipment rack alongside other BT apparatus. Click to enlarge.

Inside the MEIK

Opening the MEIK reveals the backplane PCB across the top of the enclosure and the Monolog units plugged in below via their 25-way D-type connectors. The backplane is divided into four circuit sections — one per Monolog position — each replicating the functionality of a standalone MIU. A yellow label on the right-hand side of the board indicates the link setting required for Strowger exchanges.

MEIK open showing two Monolog Mk II units and backplane PCB — MEIK open — two Mk II Monologs connected to the backplane via D-type leads. Click to enlarge.

MEIK backplane PCB showing Monolog circuits 2 and 3 with ERG relays and BT-approved components — Backplane detail — circuits 2 and 3, showing ERG relays marked 'BT APPROVED', WPS date code 9536. Click to enlarge.

MEIK backplane PCB showing Monolog circuits 3 and 4 — Backplane detail — circuits 3 and 4. ERG relays and Krone IDC punchdown blocks visible along the top edge of each circuit section. Click to enlarge.

Monolog Mk II unit labels showing serial numbers, ROM version M1-30, October 1995 — Monolog Mk II unit labels — serial nos. WPS 052521 & 052524, ROM M1-30, manufactured October 1995, Contract 644311. Click to enlarge.

MEIK Specification

Parameter	Detail
Enclosure	Lockable grey metal cabinet, wall/rack mountable
Capacity	Up to 4 Monolog units
Interface electronics	Single backplane PCB — one circuit section per Monolog position
Monolog connection	25-way D-type connector per unit
Relay type	ERG (BT Approved) — as seen on WPS 9536-dated boards
Line connections	Krone IDC punchdown blocks on backplane — 8 connections per circuit section, visible along the top edge of each PCB section
Strowger link	Link option on backplane — label fitted as reminder

NOTE

Strowger Exchange Link

The MEIK backplane carries the same meter wire link option as the standalone MIU. A yellow label inside the cabinet serves as a reminder to set the link correctly for Strowger exchanges. Refer to the MIU page for link settings by exchange type.