From CB "I've done a bit of circuit tracing on my CT34, enough to work out the memory map and options. The memory map is essentially the same as on the CT24/25 but with expansion options on RAM and ROM. The CT34 board could have up to 24k in up to 3 27C64 EPROMS or 32k in one 27C256, and either 1k, 2k or 8k static battery-backed RAM. If the 2k or 8k options were fitted only two 27C64s, i.e. up to 16K ROM could be used, or one 27C256 for the full 32k of ROM. "

PML/6 018060 Hywel's 1986 CT34 

PCB ASSEMBLY 617/04658/000 ISS 4

Chris Reports - The main PCB is the same size as the CT34 board. The case is the same as on the CT34.

The display is dot matrix. It most likely uses SPI or possibly I2C and is run over the same wiring harness as used on the CT24 and 24.

The 9-way D socket, used on CT24 & 34 for the tester, is capped and varnished over - it has never been used.

There are no less than four crystals: 2.000MHz for processor (processor can go up to 5.000MHz), 11.0592MHz for modem (IC37 - 73K222BL ), XL4 - 3.579345MHz for tone/MF4 generator,( IC29 -  phillips PCD3311CP)  and a 32.768 watch crystal for the realtime clock (IC27 Intercil ICM7170).

The processor is a CDP1806 which is an enhanced version of the 1802 with an enhanced instruction set, an onboard counter timer, and runs up to

5Mhz (1802 was 3MHZ max).

The battery is off the board: 6V 1Ah sealed "dryfit" lead acid battery. 

This CT44 board has a single 27LC512 64k byte EPROM and would use all the address space available. A fair chunk, 24k, is empty as some of the

address space must be used for RAM instead. The RAM is a 32K byte static RAM. Again, not all 32K can be used, at least not all the time.

The eprom image has human readable strings. Maintenance mode messages are only in English but public messages are in five languages: English, French, Spanish, German, and Welsh.